A-site non-stoichiometric oxygen-ion conductor fuel electrode, method of preparation and use in a solid oxide electrolysis cell

Abstract

The present application relates to a kind of A site non-stoichiometric oxygen ion conductor fuel electrode, preparation method and use in solid oxide electrolysis cell.The symmetry balance of double perovskite structure is broken by introducing A site Sr defects, not only effectively induce the in-situ desolution of B site Fe species, also significantly improve the migration rate of lattice oxygen and surface oxygen vacancy concentration.At the same time, with the increase of the reducing property of pre-treatment atmosphere (P O2 reduction), Sr 1.8 Fe 1.5 Mo 0.5 O 6‑δ Fuel electrode has experienced the change process from surface oxygen vacancy to in-situ desolution of metal Fe nanoparticles.After H2-Ar atmosphere treatment, the in-situ precipitated Fe nanoparticles form rich multi-phase interface with matrix perovskite, which not only increases more surface reaction sites, but also significantly accelerates the adsorption and activation of CO2 molecule.In addition, A site defects also enhance the thermochemical stability of the material, and promote the kinetic diffusion of internal components, which shows excellent CO2 reduction reaction performance.

Description

Technical Field

[0001] This invention relates to an A-site non-stoichiometric oxygen ion conductor fuel electrode, its preparation method, and its use in a solid oxide electrolyzer, specifically involving the oxygen ion conductor solid oxide fuel electrode material Sr. 1.8 Fe 1.5 Mo 0.5 O 6-δ The preparation method and application of this technology belong to the field of fuel cell technology. Background Technology

[0002] Against the backdrop of the current global pursuit of carbon neutrality and energy transition, the resource utilization of carbon dioxide (CO2) has become a focus of attention for both academia and industry. Solid oxide electrolyzer (SOEC) technology, with its excellent thermodynamic efficiency at high temperatures and extremely fast reaction kinetics, can efficiently convert CO2 into syngas or chemical feedstocks, and is considered a highly promising energy conversion and storage method. However, the low electrocatalytic activity of fuel electrodes in a pure CO2 atmosphere and the stability issues during long-term operation remain major bottlenecks restricting the large-scale application of SOEC. Nickel-based ceramic cathodes are widely used in SOEC for CO2 or H2O electrolysis due to their excellent catalytic activity and good thermomechanical and chemical compatibility with other battery components. However, due to the high-temperature oxidation and agglomeration of nickel-based cathodes in a pure CO2 atmosphere, their performance degrades with long-term operation, limiting their application in SOEC systems. In contrast, materials with a double perovskite structure (SFM) have become highly promising fuel electrode candidates due to their excellent redox stability, high mixed ion-electron conductivity, and good resistance to carbon deposition.

[0003] To further optimize the catalytic performance of SFM electrodes, researchers typically employ an A-site cation defect strategy to modulate their microstructure. By introducing A-site Sr defects, the stoichiometric balance of the lattice can be disrupted, thereby driving the in-situ desolvation of B-site metal elements (such as Fe) from the perovskite matrix under reducing conditions, forming highly dispersed nanoparticles with strong interactions with the matrix. This in-situ desolvation-formed metal-oxide heterointerface can significantly reduce the energy barrier required for CO2 molecule activation and provide more electrochemical active sites. However, the electrode's performance in actual electrolysis processes is highly dependent on the dynamic evolution of its surface chemical state. Different atmospheric environments with varying oxygen partial pressures, such as reducing 10% H2-Ar, inert Ar, and oxidizing pure CO2 atmospheres, will have drastically different effects on the surface reconstruction behavior of A-site defective SFMs.

[0004] Comparative studies revealed that different oxygen partial pressure environments induced varying degrees of metal desolvation and lattice oxygen defect formation, thereby altering the surface phase composition and morphology. Therefore, a deeper understanding of this intrinsic relationship between "atmosphere-structure-performance" is urgently needed. This will not only help reveal the activity enhancement mechanism of SFM electrodes in CO2 electrolysis but also provide crucial theoretical basis and experimental guidance for designing highly active and stable SOEC electrode materials through surface engineering techniques. Summary of the Invention

[0005] The technical problem to be solved by this invention is: in existing solid oxide electrolyzers (SOECs), the double perovskite structure (such as Sr2Fe) is used... 1.5 Mo 0.5 O 6-δ Although the electrode exhibits good redox stability, its intrinsic electrocatalytic activity is low in a pure CO2 environment, making it difficult to meet the requirements of high current density electrolysis. This invention prepares an A-site Sr defect double perovskite material with the general chemical formula Sr0. 2-x Fe 1.5 Mo 0.5 O 6-δ Where x ranges from 0.05 to 0.25. A multi-atmosphere induced surface reconstruction strategy is employed, utilizing A-site defects to drive in-situ desolvation of iron at B-sites to form nanoparticles, constructing a highly active heterojunction interface. Dynamic control of surface oxygen vacancies and active sites is achieved using different oxygen partial pressure atmospheres. The construction of the metal-oxide heterojunction interface significantly enhances the catalytic activity of carbon dioxide electrolysis and lowers the energy barrier for CO2 adsorption and dissociation, resulting in a significant increase in electrolysis current density. The in-situ desolvation anchoring structure endows the electrode with excellent anti-sintering and anti-carbon deposition properties, enabling reversible control of the surface microstructure according to the atmosphere, and enhancing the structural stability and service life of the electrode during long-term cyclic operation.

[0006] A non-stoichiometric oxygen ion conductor fuel electrode material at the A-site, the general chemical formula of the fuel electrode material being A₂B₂O. 6-δ The specific molecular formula is Sr 2-x Fe 1.5 Mo 0.5 O 6-δ , where δ is the content of oxygen vacancies, and x ranges from 0.05 to 0.25.

[0007] The value of x is preferably in the range of 0.1-0.2; more preferably, the molecular formula of the fuel electrode material is Sr 1.8 Fe 1.5 Mo 0.5 O 6-δ .

[0008] The fuel electrode material includes a perovskite matrix, and the surface of the perovskite matrix has in-situ dissolved Fe nanoparticles, which form a metal-oxide heterostructure with the perovskite matrix.

[0009] The preparation method of the fuel electrode material adopts the sol-gel method combined with high-temperature calcination, and includes the following steps: dissolving strontium source, iron source and molybdenum source in deionized water, heating and stirring to obtain a metal ion solution; adding a complexing agent and an alkaline pH adjuster to the metal ion solution to adjust the pH value of the solution, and continuing to heat and stir until the solution becomes a viscous gel; drying the viscous gel and then calcining it at high temperature to obtain the powder of the fuel electrode material.

[0010] The strontium source is strontium nitrate, the iron source is ferric nitrate nonahydrate, and the molybdenum source is ammonium molybdate tetrahydrate; the complexing agent includes ethylenediaminetetraacetic acid and citric acid monohydrate; and the alkaline pH adjuster is ammonia.

[0011] The molar ratio of ethylenediaminetetraacetic acid, citric acid monohydrate, and total metal ions is 1:1.5-2.5:0.5-1.5; in the step of adjusting the pH value of the solution, the adjusted pH value is 6-8, preferably 7-8.

[0012] The drying conditions are: baking at 140-180℃ for 1-10 hours, and the high-temperature calcination conditions are: calcination at 900-1200℃ for 5-10 hours, with a heating rate of 2-8℃ / min.

[0013] It also includes an atmosphere-induced surface reconstruction step: the powder of the fuel electrode material obtained after high-temperature calcination is heat-treated in a hydrogen-containing reducing mixed atmosphere to induce in-situ desolvation of Fe elements at B sites to form metallic Fe nanoparticles; the hydrogen-containing reducing mixed atmosphere is a 5-15% H2-Ar mixture; the temperature and time of the heat treatment are set according to actual needs, preferably 2-10 hours at 800-900℃.

[0014] The application of the fuel electrode material in solid oxide electrolyzers.

[0015] The fuel electrode material serves as the fuel electrode in a solid oxide electrolyzer for the electrochemical conversion of CO2 into CO. The solid oxide electrolyzer includes an electrolyte and an air electrode, wherein the electrolyte is La. 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ Where δ represents the oxygen vacancy content; the air electrode is PrBa 0.5 Sr 0.5 Co 1.5 Fe0.5 O 6-δ Where δ represents the oxygen vacancy content; the electrolysis current density of the fuel electrode material reaches 2.50 Acm under pure CO2 atmosphere, 850℃ and 1.6V voltage conditions. -2 Furthermore, the activation energy barrier for the CO2 reduction reaction is reduced to below 1.30 eV.

[0016] The beneficial effects of this invention are:

[0017] (1) This invention synthesizes Sr by combining the sol-gel method and the high-temperature calcination method. 1.8 Fe 1.5 Mo 0.5 O 6-δ (SFM18) electrode material, the elements in the material are uniformly distributed, and the synthesis method is simple and efficient.

[0018] (2) The chemical driving force generated by the Sr defect at the A site induces the in-situ desolvation of Fe element at the B site under reducing conditions, forming a high-density nanoscale metal-oxide heterostructure. These interfaces, as highly efficient active centers, significantly reduce the energy barrier for CO2 molecule adsorption and activation.

[0019] (3) By utilizing surface reconstruction strategies induced by different atmospheres (CO2, Ar, 10% H2-Ar), the electrode can dynamically adjust the oxygen vacancy concentration and component distribution according to actual electrolysis conditions. This environmental responsiveness provides great flexibility for optimizing the electrode's performance under different oxygen partial pressures. 1.8 Fe 1.5 Mo 0.5 O 6-δ SFM18, as an excellent fuel electrode material, was used in a single SFM18|LSGM|PBSCF cell. After treatment with 10% H2-Ar in electrolysis mode, the cell was successfully electrolyzed at 850 °C. 0 At C and 1.6 V, the current density for electrolyzing CO2 is 2.68 A cm⁻¹. -2 .

[0020] (4) The design of the A-site defect not only promotes the precipitation of functional components, but also enhances the mechanical stability of the material in the oxidation-reduction cycle by adjusting the internal stress of the lattice, effectively avoiding the cracking of the electrode layer or its detachment from the electrolyte surface during long-term operation, thus extending the battery's service life. Attached Figure Description

[0021] Figure 1 The images show the XRD patterns of SFM18 and electrode materials treated with Ar (SFM18-Ar) and 10% H2-Ar (SFM18-H2 / Ar) at room temperature.

[0022] Figure 2 It is SFM18, SFM18-Ar and SFM18-H2 / Ar at 850 0 C, XRD pattern after treatment in pure CO2 atmosphere for 10 h;

[0023] Figure 3 It is SFM18 electrode material and at 850 0 SEM image of C after treatment with Ar or 10% H2-Ar for 5 h;

[0024] Figure 4 XPS spectra of O1S and Fe2p in SFM18, SFM18-Ar and SFM18-H2 / Ar;

[0025] Figure 5 The attached diagram shows the CO2 temperature-programmed desorption process for SFM18, SFM18-Ar, and SFM18-H2 / Ar.

[0026] Figure 6 These are the infrared spectra of SFM18, SFM18-Ar, and SFM18-H2 / Ar;

[0027] Figure 7 Impedance diagrams of SFM18, SFM18-Ar and SFM18-H2 / Ar electrode materials obtained on symmetrical cells at 850-700 °C and 50% CO-CO2 atmosphere;

[0028] Figure 8 Arrhenius diagrams of SFM18, SFM18-Ar and SFM18-H2 / Ar electrode materials were obtained on symmetric cells at 850-700 °C and 50% CO-CO2 atmosphere;

[0029] Figure 9 The impedance comparison diagrams and corresponding DRT treatments of SFM18, SFM18-Ar and SFM18-H2 / Ar electrode materials obtained on symmetrical cells at 850 °C and 50% CO-CO2 atmosphere are shown.

[0030] Figure 10 These are the IV curves and impedance diagrams at 1.5 V for the SFM18|LSGM|PBSGF electrolyzer in electrolytic cell mode within the temperature range of 700-850 °C.

[0031] Figure 11 These are the IV curves and impedance diagrams at 1.5 V for an SFM18-Ar|LSGM|PBSGF electrolyzer in electrolytic cell mode within the temperature range of 700-850 °C.

[0032] Figure 12These are the IV curves and impedance diagrams at 1.5 V for the SFM18-H2 / Ar|LSGM|PBSGF electrolyzer in electrolytic cell mode within the temperature range of 700-850 °C.

[0033] Figure 13 This is a comparison chart of the electrolysis performance of single cells using SFM18, SFM18-Ar, and SFM18-H2 / Ar as fuel electrodes at 750-850 °C and 1.6V.

[0034] Figure 14 The image shows the SEM morphology of a single cell tested with SFM18-H2 / Ar as the fuel electrode. Detailed Implementation

[0035] This invention provides an oxygen ion conductor solid oxide electrolyzer fuel electrode material Sr with excellent electrochemical performance. 2-x Fe 1.5 Mo 0.5 O 6-δ The preparation method and application of Sr, where x ranges from 0.05 to 0.25, and δ represents the oxygen vacancy content, belong to the field of solid oxide electrolytic cell fuel electrode materials. Sr was synthesized by a combination of sol-gel method and high-temperature calcination method. 1.8 Fe 1.5 Mo 0.5 O 6-δ The (SFM18) electrode material exhibits a uniform distribution of elements within its structure. Its synthesis is simple and efficient. The chemical driving force generated by Sr defects at the A-site induces in-situ desolvation of Fe elements at the B-site under reducing conditions, forming a high-density nanoscale metal-oxide heterostructure. These interfaces, acting as highly efficient active centers, significantly lower the energy barrier for CO2 molecule adsorption and activation. Utilizing surface reconstruction strategies induced by different atmospheres (CO2, Ar, 10% H2-Ar), the electrode can dynamically adjust the oxygen vacancy concentration and component distribution according to actual electrolysis conditions. This environmental responsiveness provides significant flexibility for optimizing the electrode's performance under varying oxygen partial pressures. 1.8 Fe 1.5 Mo 0.5 O 6-δ SFM18, as an excellent fuel electrode material, was used in a single SFM18|LSGM|PBSCF cell. After treatment with 10% H2-Ar in electrolysis mode, the cell was successfully electrolyzed at 850 °C. 0 At C and 1.6 V, the current density for electrolyzing CO2 is 2.68 A cm⁻¹. -2 This invention develops a high-performance oxygen ion conductor solid oxide fuel electrode material and its preparation method, which greatly improves the electrochemical performance and long-term stability of solid oxide electrolyzers.

[0036] Some embodiments of this patent include the following technical solutions:

[0037] The first aspect of the present invention provides:

[0038] A solid oxide fuel electrode material for oxygen ion conductors, characterized in that the general chemical formula of the material is A₂B₂O. 6-δ The specific molecular formula is: Sr 2-x Fe 1.5 Mo 0.5 O 6-δ , where δ is the content of oxygen vacancies, x = 0.05-0.25, preferably 0.1-0.2.

[0039] In one embodiment, the molecular formula is: Sr 1.8 Fe 1.5 Mo 0.5 O 6-δ (SFM18).

[0040] A second aspect of the invention provides:

[0041] The preparation method of the oxygen ion conductor solid oxide fuel electrode material mentioned above refers to the gel sol method combined with high-temperature calcination.

[0042] The above-mentioned method for preparing oxygen ion conductor solid oxide fuel electrode material is characterized by comprising the following steps: sequentially mixing Sr(NO3)2, Fe(NO3)3.9H2O and (NH4)6Mo7O according to the mass ratio and stoichiometric ratio. 24 . 4H2O is dissolved together in deionized water and heated and stirred until homogeneous. A certain proportion of ethylenediaminetetraacetic acid, citric acid monohydrate and ammonia water are poured into the solution, the pH is adjusted to about 6-8, and the solution is heated and stirred until it becomes a viscous gel state. After drying, it is calcined to obtain powder.

[0043] In one embodiment, the molar ratio of ethylenediaminetetraacetic acid:citric acid monohydrate:total metal ions is 1:2:1.

[0044] In one embodiment, the drying conditions are baking at 140-180 °C for 1-10 h.

[0045] In one embodiment, the calcination temperature is 900-1200°C. o Calcination at C for 5-10 hours, with a heating rate of 2-8°C. o C / min.

[0046] A third aspect of the invention provides:

[0047] The above-mentioned oxygen ion conductor solid oxide fuel electrode material is used in solid oxide electrolytic cells.

[0048] The application described is as a fuel electrode.

[0049] In one embodiment, the aforementioned uses are to improve the CO2 adsorption capacity of the electrode material, enhance CO2RR activity, current output performance, and improve battery durability.

[0050] A fourth aspect of the present invention provides:

[0051] A high-temperature solid oxide electrolytic cell supported by an oxygen ion conductor electrolyte includes the following steps:

[0052] Electrolyte powder is first pressed to prepare an electrolyte support layer, and then sintered to densify the electrolyte layer. Then, SFM18 fuel electrode and PBSCF air electrode are sprayed on both sides of the electrolyte to obtain an SFM18|LSGM|PBSCF single cell. The cell is then calcined again to obtain the battery cell.

[0053] In one embodiment, the electrolyte used in the aforementioned solid oxide electrolytic cell is La. 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ (LSGM).

[0054] In one embodiment, the calcination parameters for the electrolyte are 1450 °C for 5 h.

[0055] In one embodiment, the single cell is calcined at 1000 °C for 2 h.

[0056] Example 1

[0057] This embodiment provides an oxygen ion conductor solid oxide electrolyzer fuel electrode material, using Sr 1.8 Fe 1.5 Mo 0.5 O 6-δ Taking the preparation method of -10% H2 / Ar (SFM18-H2 / Ar) as an example, the specific steps are as follows:

[0058] (1) Weigh out 7.6187 g of strontium nitrate, 12.1201 g of ferric nitrate nonahydrate and 1.7655 g of ammonium molybdate tetrahydrate, and dissolve them in an appropriate amount of deionized water. Weigh out 22.211 g of ethylenediaminetetraacetic acid and 31.942 g of citric acid monohydrate as complexing agents according to the molar ratio of ethylenediaminetetraacetic acid:citric acid monohydrate:metal ions = 1:2:1, and add an appropriate amount of deionized water.

[0059] (2) Add the obtained complexing agent to the dissolved metal ion solution, and then add an appropriate amount of ammonia water to adjust the pH range of the solution to 7-8. Then heat and stir until the water evaporates to obtain a gel-like substance.

[0060] (3) The gel-like substance was placed in a forced-air drying oven and dried at 180 °C for 5 h to obtain the desired foam-like precursor.

[0061] (4) The obtained precursor was calcined in a high-temperature furnace at 1100 °C for 10 h to finally obtain Sr 1.8 Fe 1.5 Mo 0.5 O 6-δ (SFM18) powder.

[0062] (5) The obtained powder is treated in a tube furnace at 850 °C for 5 h in a 10% H2 / Ar atmosphere to obtain SFM18-H2 / Ar powder.

[0063] Example 2

[0064] This embodiment provides a method for preparing and testing a symmetrical cell using SFM18-H2 / Ar as the electrode. The specific steps are as follows:

[0065] (1) Weigh 1 g of the electrode powder SFM18-H2 / Ar prepared in Example 1 into a high-energy spherical ink jar, and add 10 mL of isopropanol, 2 mL of ethylene glycol and 0.8 mL of glycerol. After ball milling at 400 r / min for 30 min, the desired electrode slurry is obtained.

[0066] (2) The prepared LSGM electrolyte sheet was placed on a heating stage at 150 °C. The prepared electrode slurry was uniformly sprayed onto both sides of the electrolyte sheet using an inert gas and a spray gun. After the liquid had completely evaporated, the sprayed electrolyte sheet was placed in a high-temperature furnace at 1000 °C for 2 h to obtain the desired symmetrical cell. The electrode polarization impedance was then tested in the temperature range of 700-850 °C. After the temperature stabilized at 850 °C, the cell was treated with 10% H2-Ar for 60 minutes, followed by a 2-minute switch to a 50% CO-CO2 atmosphere before testing. The polarization impedance of the symmetrical cell measured at 850 °C in a 50% CO-CO2 atmosphere was 0.165 Ω cm. 2 .

[0067] Example 3

[0068] This embodiment provides a method for preparing and testing a single cell using SFM18-H2 / Ar as the fuel electrode. The specific steps are as follows:

[0069] (1) Weigh 1 g of the electrode powder SFM18-H2 / Ar prepared in Example 1 into a high-energy spherical ink jar, and add 10 mL of isopropanol, 2 mL of ethylene glycol and 0.8 mL of glycerol. After ball milling at 400 r / min for 30 min, the desired electrode slurry is obtained.

[0070] (2) The prepared PBSCF-LSGM half-cell sheet was placed on a heating stage at 150 °C. The prepared electrode slurry was uniformly sprayed onto the electrolyte side surface using an inert gas and a spray gun. After the liquid completely evaporated, the sprayed electrolyte sheet was placed in a high-temperature furnace at 1000 °C for 2 h to obtain the desired single cell. The cell was then used to test the CO2 electrolysis performance of the battery within a temperature range of 750-850 °C. The heating process used CO2 for heating. After reaching a stable temperature of 850 °C, the battery was treated with 10% H2-Ar for 60 minutes, followed by a 2-minute CO2 atmosphere before testing. The current density obtained by the battery in electrolysis mode at 850 °C and 1.6 V was -2.679 A cm⁻¹. -2 .

[0071] Comparative Example 1

[0072] This comparative example provides an oxygen ion conductor solid oxide electrolyzer fuel electrode material for Sr. 1.8 Fe 1.5 Mo 0.5 O 6-δ Taking the preparation method of (SFM18) as an example, the specific steps are as follows:

[0073] (1) Weigh out 7.6187 g of strontium nitrate, 12.1201 g of ferric nitrate nonahydrate and 1.7655 g of ammonium molybdate tetrahydrate, and dissolve them in an appropriate amount of deionized water. Weigh out 22.211 g of ethylenediaminetetraacetic acid and 31.942 g of citric acid monohydrate as complexing agents according to the molar ratio of ethylenediaminetetraacetic acid:citric acid monohydrate:metal ions = 1:2:1, and add an appropriate amount of deionized water.

[0074] (2) Add the obtained complexing agent to the dissolved metal ion solution, and then add an appropriate amount of ammonia water to adjust the pH range of the solution to 7-8. Then heat and stir until the water evaporates to obtain a gel-like substance.

[0075] (3) The gel-like substance was placed in a forced-air drying oven and dried at 180 °C for 5 h to obtain the desired foam-like precursor.

[0076] (4) The obtained precursor was calcined in a high-temperature furnace at 1100 °C for 10 h to finally obtain Sr 1.8 Fe 1.5 Mo0.5 O 6-δ (SFM18) powder.

[0077] Comparative Example 2

[0078] This comparative example provides an oxygen ion conductor solid oxide electrolyzer fuel electrode material for Sr. 1.8 Fe 1.5 Mo 0.5 O 6-δ Taking the preparation method of -Ar (SFM18-Ar) as an example, the specific steps are as follows:

[0079] (1) Weigh out 7.6187 g of strontium nitrate, 12.1201 g of ferric nitrate nonahydrate and 1.7655 g of ammonium molybdate tetrahydrate, and dissolve them in an appropriate amount of deionized water. Weigh out 22.211 g of ethylenediaminetetraacetic acid and 31.942 g of citric acid monohydrate as complexing agents according to the molar ratio of ethylenediaminetetraacetic acid:citric acid monohydrate:metal ions = 1:2:1, and add an appropriate amount of deionized water.

[0080] (2) Add the obtained complexing agent to the dissolved metal ion solution, and then add an appropriate amount of ammonia water to adjust the pH range of the solution to 7-8. Then heat and stir until the water evaporates to obtain a gel-like substance.

[0081] (3) The gel-like substance was placed in a forced-air drying oven and dried at 180 °C for 5 h to obtain the desired foam-like precursor.

[0082] (4) The obtained precursor was calcined in a high-temperature furnace at 1100 °C for 10 h to finally obtain Sr 1.8 Fe 1.5 Mo 0.5 O 6-δ (SFM18) powder.

[0083] (5) The obtained powder is treated in a tube furnace at 850 °C for 5 h in an Ar atmosphere to obtain SFM18-Ar powder.

[0084] Characterization results

[0085] 1. X-ray diffraction (XRD) characterization

[0086] Figure 1 These are the XRD patterns of three electrode powders, SFM18, SFM18-Ar, and SFM18-H2 / Ar, at room temperature. All three samples exhibit typical diffraction peaks of perovskite oxides (PDF#96-153-1826), with no other impurity peaks. All diffraction peaks are sharp, indicating a high degree of crystallinity in the powder.

[0087] Figure 2 It is SFM18, SFM18-Ar and SFM18-H2 / Ar at 850 0 C, XRD patterns after treatment in a pure CO2 atmosphere for 10 h; all three samples exhibited the same phase structure as before treatment, indicating that the three electrode materials can maximize the stability of the electrode materials while providing mixed ion electronic conductivity for the fuel electrode under a CO2 atmosphere. This verifies the good anti-carbon deposition ability of the three electrode materials.

[0088] 2. Scanning electron microscopy (SEM) characterization

[0089] Figure 3 It is SFM18 powder electrode material and at 850 0 Three powder electrode materials, SFM18, SFM18-Ar, and SFM18-H2 / Ar, were obtained after C was treated with Ar or 10% H2-Ar for 5 h. SEM images of each material after 0.5 g of each was obtained after pressing and sintering. The SEM images clearly show that (Figure a) the SFM18 electrode exhibits a typical polycrystalline perovskite morphology with clear and uniformly distributed grain boundaries. The grain surface is very smooth, with no secondary phases or nanoparticles precipitated. This indicates that in an oxidizing atmosphere, A-site defects are accommodated by the lattice, and the system is in a thermodynamically stable state. (Figure b) The SFM18-Ar electrode shows that after treatment in an Ar atmosphere, its morphology is basically consistent with the original state. Although slight thermal etching due to heat treatment may have resulted in slightly deeper grain boundaries, the surface remains clean, and no obvious surface reconstruction or particle precipitation was observed. This indicates that the neutral atmosphere is insufficient to drive the reduction and migration of B-site cations. (Figure c) The SFM18-H2 / Ar electrode shows a drastic change in morphology. A large number of high-density, spherical nanoparticles of varying sizes (typically metallic Fe) precipitated in situ on the surface. The particles exhibit a distribution ranging from a few nanometers to hundreds of nanometers and are firmly embedded in the surface of the perovskite matrix.

[0090] 3. X-ray photoelectron spectroscopy (XPS) characterization

[0091] Figure 4 XPS spectra of O1s-Fe2p combination in SFM18, SFM18-Ar, and SFM18-H2 / Ar electrode materials; lattice oxygen (O2) in SFM18-H2 / Ar. lattice ) and adsorbed oxygen (O adsorb The contents of O2 were 21.81% and 78.19% respectively, while the contents of O2 in SFM18-H2 / Ar and SFM18 samples were... adsorb / O lattice The values ​​were 3.59 and 1.97, respectively, indicating that treatment in a 10% H2 / Ar atmosphere resulted in more oxygen vacancies. Fe 2p 3 / 2Fe exhibits at binding energies of 706.8, 709.8, 710.8, and 711.9 eV, respectively. 0 Fe 2+ Fe 3+ and Fe 4+ Four valence states were observed, demonstrating the precipitation of Fe nanoparticles under a reducing atmosphere. Compared to SFM18, the average valence state of Fe decreased from +2.89 to +2.35. To achieve electron neutralization, the decrease in cation valence state is accompanied by the formation of oxygen vacancies. This indicates that treatment in a 10% H2 / Ar atmosphere resulted in a rich multiphase interface between the in-situ precipitated Fe nanoparticles and the parent perovskite, which increased the number of surface reaction sites.

[0092] 4. Characterization of CO2 temperature-programmed desorption (CO2-TPD)

[0093] Figure 5 The three materials are SFM18, SFM18-Ar and SFM18-H2 / Ar, which are pre-treated at 300°C. o C. After adsorption under a pure CO2 atmosphere for two hours, the material was monitored using QMS 403 Aё (Netzsch, Germany) from room temperature to 1000°C. o The CO2 desorption signal during the C process (CO2-TPD) is shown. The CO2 desorption behavior of the three materials is similar, at 300... 0 CO2 desorption occurring above temperature is due to the chemical adsorption of CO2 by the material. SFM18-H2 / Ar has the highest desorption temperature, which is closer to the operating temperature of an actual electrolytic cell. Furthermore, judging from the peak area of ​​the CO2 desorption curve, the SFM18-H2 / Ar material has a high energy barrier for the adsorption and activation of CO2 molecules, which is beneficial to improving the CO2 RR process of the material.

[0094] 5. Infrared (IR) spectral characterization

[0095] Figure 6 These are the infrared spectra of SFM18, SFM18-Ar, and SFM18-H2 / Ar electrode materials after CO2 adsorption treatment. The spectra are located in the 1430-1500 cm⁻¹ range. -1 A distinct peak appears at this point, and this peak usually corresponds to... The presence of [something]. Under the same adsorption treatment conditions, it is noteworthy that, compared with the original sample, the peak intensity of the sample pre-reduced by SFM18-H2 / Ar was significantly reduced in these regions. This indicates that the in-situ desoluble Fe nanoparticles effectively promoted the rapid conversion of carbonate to CO, thereby inhibiting the excessive accumulation of stable carbonate intermediates.

[0096] 6. Electrochemical impedance spectroscopy

[0097] Figure 7These are impedance diagrams obtained on symmetrical cells using SFM18, SFM18-Ar, and SFM18-H2 / Ar electrode materials at 850-700 °C in a 50% CO-CO2 atmosphere. It is evident that the polarization impedance of the symmetrical cell increases with decreasing test temperature, indicating that the CO2 RR in the solid oxide electrolyzer is significantly affected by temperature, and that higher temperatures promote CO2 activation.

[0098] Figure 8 Arrhenius plots were obtained for SFM18, SFM18-Ar, and SFM18-H2 / Ar electrode materials on symmetric cells at 850-700 °C under a 50% CO-CO2 atmosphere. The exsolution of more Fe nanoparticles effectively reduced the activation energy barrier of CO2RR from 1.30 eV (SFM18) to 1.28 eV (SFM18-H2 / Ar), which confirms that treatment in a 10% H2 / Ar atmosphere can effectively enhance the electrode's activation ability for CO2.

[0099] Figure 9 Impedance comparison diagrams and corresponding DRT treatments are shown for SFM18, SFM18-Ar, and SFM18-H2 / Ar electrode materials obtained on symmetrical cells at 850 °C in a 50% CO-CO2 atmosphere. In a 50% CO-CO2 atmosphere, the ASR of the SFM18, SFM18-Ar, and SFM18-H2 / Ar electrode materials at 850 °C are 0.25, 0.27, and 0.17 Ω cm, respectively. 2 Among them, SFM18-H2 / Ar had the lowest ASR, reducing it by approximately 32% compared to SFM materials. From the corresponding DRT results, treatment with a 10% H2 / Ar atmosphere significantly reduced O2 in the mid-frequency region. 2- The peak intensity of ion migration at the cathode indicates that SFM18-H2 / Ar effectively promotes the rapid conversion of carbonate to CO, thereby enhancing catalytic activity and accelerating reaction kinetics, thus reducing the reaction impedance in the mid-frequency region.

[0100] 7. Electrolyte performance testing

[0101] Figure 10 , Figure 11 and Figure 12 These are SFM18|LSGM|PBSCF, SFM18-Ar|LSGM|PBSCF, and SFM18-H2 / Ar|LSGM|PBSCF electrolyzers at 100 mL / min. -1The temperature was increased to 850 °C under a pure CO2 atmosphere, and the temperature was decreased in 50 °C increments to obtain IV curves in electrolytic cell mode within the temperature range of 750-850 °C. The electrolysis product was CO. The SFM18|LSGM|PBSCF electrolytic cell was heated to 850 °C in 100 mL / min. -1 In a pure CO2 atmosphere, the current densities at 750, 800, and 850 °C are -0.75, -1.40, and -2.30 A cm⁻¹, respectively. -2 (1.5 V). The current densities of SFM18-Ar|LSGM|PBSCF under the same conditions were -0.61, -1.55, and -2.37 A cm⁻¹, respectively. -2 (1.5 V). The current densities of SFM18-H2 / Ar|LSGM|PBSCF under the same conditions were -0.92, -1.61, and -2.61 A cm⁻¹, respectively. -2 (1.5 V). It can be seen that the current density of the SFM18-H2 / Ar fuel electrode is much higher than that of the SFM18 and SFM18-Ar electrodes in the temperature range of 750-850 °C.

[0102] Figure 13 This chart compares the electrolytic performance of three electrolytic cells using SFM18, SFM18-Ar, and SFM18-H2 / Ar as electrode materials, respectively, under the same heating conditions and testing methods, within the temperature range of 750-850 °C. At 850 °C under the same atmosphere, the current densities of the SFM18, SFM18-Ar, and SFM18-H2 / Ar electrode materials are -2430, -2450, and -2679 mAcm, respectively. -2 (1.6 V); It can be seen that the current output of the SFM18-H2 / Ar electrode material is at its maximum at three temperature points of 750, 800 and 850 °C, indicating that more active centers are formed under 10% H2 / Ar reduction, which improves the catalytic activity of the battery and can achieve higher electrochemical performance.

[0103] Figure 14 This is a SEM image of the SFM18-H2 / Ar|LSGM|PBSCF after testing. It can be seen that the LSGM electrolyte thickness is approximately 250 μm, and the SFM18-H2 / Ar fuel electrode thickness is approximately 20 μm. The surface microstructure of the tested fuel electrode remains porous and smooth, and the electrode is tightly bonded to the LSGM electrolyte; no obvious electrode detachment or delamination was observed.

Claims

1. A non-stoichiometric oxygen ion conductor fuel electrode material at the A-site, characterized in that, The chemical formula of the fuel electrode material is A2B2O. 6-δ The specific molecular formula is Sr 2-x Fe 1.5 Mo 0.5 O 6-δ , where δ is the content of oxygen vacancies, and x ranges from 0.05 to 0.

25.

2. The fuel electrode material according to claim 1, characterized in that, The value of x is preferably in the range of 0.1-0.2; more preferably, the molecular formula of the fuel electrode material is Sr 1.8 Fe 1.5 Mo 0.5 O 6-δ .

3. The fuel electrode material according to claim 1 or 2, characterized in that, The fuel electrode material includes a perovskite matrix, and the surface of the perovskite matrix has in-situ dissolved Fe nanoparticles, which form a metal-oxide heterostructure with the perovskite matrix.

4. A method for preparing a fuel electrode material as described in any one of claims 1-3, characterized in that, The preparation method employs a sol-gel method combined with high-temperature calcination, comprising the following steps: dissolving strontium, iron, and molybdenum sources in deionized water, heating and stirring until homogeneous to obtain a metal ion solution; adding a complexing agent and an alkaline pH adjuster to the metal ion solution to adjust the pH value of the solution, and continuing to heat and stir until the solution becomes a viscous gel; drying the viscous gel and then calcining it at high temperature to obtain the powder of the fuel electrode material.

5. The preparation method according to claim 4, characterized in that, The strontium source is strontium nitrate, the iron source is ferric nitrate nonahydrate, and the molybdenum source is ammonium molybdate tetrahydrate; the complexing agent includes ethylenediaminetetraacetic acid and citric acid monohydrate; and the alkaline pH adjuster is ammonia.

6. The preparation method according to claim 5, characterized in that, The molar ratio of ethylenediaminetetraacetic acid, citric acid monohydrate, and total metal ions is 1:1.5-2.5:0.5-1.5; in the step of adjusting the pH value of the solution, the adjusted pH value is 6-8, preferably 7-8.

7. The preparation method according to claim 4, characterized in that, The drying conditions are: baking at 140-180℃ for 1-10 hours, and the high-temperature calcination conditions are: calcination at 900-1200℃ for 5-10 hours, with a heating rate of 2-8℃ / min.

8. The preparation method according to claim 4, characterized in that, It also includes an atmosphere-induced surface reconstruction step: the powder of the fuel electrode material obtained after high-temperature calcination is heat-treated in a hydrogen-containing reducing mixed atmosphere to induce in-situ desolvation of Fe elements at B sites to form metallic Fe nanoparticles; the hydrogen-containing reducing mixed atmosphere is a 5-15% H2-Ar mixture; the temperature and time of the heat treatment are set according to actual needs, preferably 2-10 hours at 800-900℃.

9. Use of a fuel electrode material as described in any one of claims 1-3 in a solid oxide electrolyzer.

10. The use according to claim 9, characterized in that, The fuel electrode material serves as the fuel electrode in a solid oxide electrolyzer for the electrochemical conversion of CO2 into CO. The solid oxide electrolyzer includes an electrolyte and an air electrode, wherein the electrolyte is La. 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ Where δ represents the oxygen vacancy content; the air electrode is PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 6-δ Where δ represents the oxygen vacancy content; the electrolysis current density of the fuel electrode material reaches 2.50 Acm under pure CO2 atmosphere, 850℃ and 1.6V voltage conditions. -2 Furthermore, the activation energy barrier for the CO2 reduction reaction is reduced to below 1.30 eV.

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