A method of characterizing a solid oxide fuel cell / electrolysis cell air electrode

Abstract

This invention relates to a characterization method for air electrodes in solid oxide fuel cells / electrolytes. The cross-section of the air electrode is divided into multiple test sites from the electrode / electrolyte interface to the surface. K-edge near-edge absorption spectra of active site elements at each test site are collected using a synchrotron radiation micro-area beamline. By comparing the absorption spectrum characteristics under different operating conditions, the changes in elemental valence states and the degree of electrode attenuation are determined. This method, through gradient site division combined with micro-area testing, achieves quantitative determination of valence state changes of active site elements. Starting from the intrinsic fundamental factors of electrode attenuation, it overcomes the limitation of existing technologies that can only obtain superficial information. It can accurately capture the valence state gradient change law in the electrode thickness direction, clearly distinguish the electrode influence mechanism of different operating modes, and achieve accurate characterization of electrode attenuation. This provides a direct and effective theoretical basis and technical support for the material optimization and structural design of air electrodes.

Description

Technical Field

[0001] This invention relates to characterization methods, and more specifically to a characterization method for an air electrode of a solid oxide fuel cell / electrolyte. Background Technology

[0002] Solid oxide fuel cells (SOFCs) and their reverse process, solid oxide electrolyzers (SOECs), are energy conversion devices with great potential. Their long-term operational stability directly determines the device's performance and lifespan. The degradation of electrode materials during operation is a key bottleneck restricting the development and commercial application of SOFC / SOEC technology. Therefore, accurate and effective characterization of electrode degradation is crucial for a deeper understanding of the intrinsic mechanisms of battery aging, optimizing battery structure design, and improving the long-term operational stability of batteries.

[0003] Currently, the main characterization methods for SOFC / SOEC electrode degradation in the industry include electrochemical impedance spectroscopy (EIS), galvanostatic polarization, and scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy (EDS). Although these methods can obtain relevant information about the electrode under different operating conditions from different perspectives, they all have significant limitations and cannot comprehensively and deeply reflect the core issues of electrode degradation. For example, EIS can distinguish between ohmic impedance caused by ion conduction and polarization impedance related to electrode reactions, but the various physicochemical processes contained in polarization impedance have a high degree of overlap, making further decomposition and analysis difficult and unable to accurately locate the causes of degradation. The combination of SEM and EDS can only provide information on the microstructure and elemental distribution of the electrode, and cannot directly reflect the correlation between changes in the electrode's chemical state and the degradation of its electrochemical performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies that only provide information on the apparent performance or structure of electrodes, failing to directly reflect the underlying factors of electrode degradation and accurately characterize the electrode degradation patterns under different operating modes, this invention aims to provide a characterization method for air electrodes in solid oxide fuel cells / electrolytes.

[0005] The present invention relates to a characterization method for an air electrode in a solid oxide fuel cell / electrolyte, used to characterize the valence state changes of active site elements in the air electrode before and after operation in power generation (FC) and electrolysis (EC) modes, respectively. The method includes the following steps: S1, dividing the cross-section of the air electrode from the electrode / electrolyte interface to the electrode surface into multiple test sites; S2, using a synchrotron radiation micro-area beamline with spatial resolution, collecting the K-edge near-edge absorption spectra of active site elements at each test site of the air electrode; S3, comparing the K-edge near-edge absorption spectrum characteristics of each test site under different operating conditions to determine the valence state changes of the active site elements, and thus determining the degree of attenuation of the air electrode.

[0006] To address the shortcomings of existing SOFC / SOEC electrode attenuation characterization methods, which only obtain apparent performance or structural information, fail to directly reflect the fundamental factors of electrode attenuation, and are difficult to accurately characterize electrode attenuation patterns under different operating modes, this invention achieves characterization of valence state changes at active sites and determination of electrode attenuation through site division, comparison of K-edge near-edge absorption spectra measured by synchrotron radiation micro-area beamlines and spectra under different operating conditions. Starting from the intrinsic factor of valence state changes at active sites, this invention establishes an accurate characterization method for electrode attenuation, which can directly reflect the core reasons for electrode attenuation and provide a fundamental basis for electrode optimization.

[0007] In a preferred embodiment, in step S1, the test sites are arranged sequentially along the thickness direction of the air electrode from the electrode / electrolyte interface to the electrode surface, including a first test site near the electrode / electrolyte interface, a fourth test site near the electrode surface, and at least one intermediate test site located between the first and fourth test sites; wherein, the first test site is the site closest to the electrode / electrolyte interface and farthest from the electrode surface, and the fourth test site is the site farthest from the electrode / electrolyte interface and closest to the electrode surface. Considering that existing characterization methods cannot achieve precise micro-area characterization of different depth regions of the electrode and cannot reflect the attenuation gradient differences along the thickness direction of the air electrode, this invention arranges test sites along the thickness direction of the air electrode, distinguishing between near-interface, near-surface, and intermediate sites, matching the gradient distribution characteristics of the electrode electrochemical reaction, so that the test sites correspond to the intensity distribution of the electrode electrochemical reaction, accurately capturing the valence state changes of active sites in different depth regions of the electrode, and reflecting the attenuation gradient law along the thickness direction of the air electrode.

[0008] In a preferred embodiment, in step S1, four test sites are set, namely P1, P2, P3, and P4, where P1 is the first test site, P4 is the fourth test site, and P2 and P3 are the intermediate test sites, uniformly distributed along the thickness direction of the air electrode. This invention establishes a standardized and repeatable method for dividing electrode micro-region test sites by quantifying the test sites into four uniformly distributed sites, ensuring that test results from different experiments and different electrode samples can be compared, and improving the versatility and accuracy of the characterization method.

[0009] In a preferred embodiment, the air electrode is a Co-based perovskite material, the active site element is Co, and the Co-based perovskite material is an ABO3-type single perovskite material containing Co at the B-site or an AA′B2O6-type double perovskite structure material. This invention, by limiting the air electrode to a Co-based perovskite material and the active site element to Co, which plays a major catalytic role, selects Co as the core catalytic element for the mainstream high-performance Co-based perovskite air electrode in SOFC / SOEC, ensuring high sensitivity of the absorption spectrum to valence state changes and meeting the characterization requirements of mainstream electrode materials.

[0010] In a preferred embodiment, the ABO3-type single perovskite material is BSCF, and the AA′B2O6-type double perovskite structure material is PBCC. This invention, by clearly defining Co-based perovskite materials, provides specific and directly implementable characterization objects for two typical Co-based perovskite air electrode materials used in practical SOFC / SOEC applications, thereby improving the practicality and applicability of the method.

[0011] In a preferred embodiment, in step S3, the valence state change of the active site element is determined by comparing the energy shift of the K-side near-side absorption spectrum within the normalized absorption intensity range of 0.7 to 0.9. The valence state of the active site element is linearly positively correlated with the energy shift of the absorption spectrum within this range; when the valence state increases, the energy position of the absorption spectrum shifts towards higher energy, and when the valence state decreases, the energy position of the absorption spectrum shifts towards lower energy. This invention, by limiting the normalized absorption intensity range to 0.7 to 0.9, selects the observation range that is most sensitive to and has the strongest anti-interference capability for changes in the valence state of the active site element. Utilizing the linear relationship between valence state and spectral line shift, it achieves accurate quantitative determination of the valence state change of the active site element, improving the accuracy of attenuation characterization.

[0012] In a preferred embodiment, the normalized absorption intensity range of 0.7 to 0.9 is the core observation window for Co element valence state analysis, suitable for testing valence state changes of Co from +2 to +4. This invention, by defining the 0.7 to 0.9 range as the dedicated core observation window for Co, ensures that the observation range precisely matches the actual valence state change range of Co during SOFC / SOEC operation, guaranteeing the sensitivity and accuracy of testing Co element valence state changes and accurately capturing the details of valence state changes during electrode operation.

[0013] In a preferred embodiment, step S3 includes different operating conditions before the reaction, after FC mode testing, and after EC mode testing. By comparing the K-edge near-edge absorption spectrum characteristics of each test site under the three operating conditions, the influence of FC mode and EC mode on the air electrode is determined. This invention, through spectral comparison of the three operating conditions, can clearly distinguish the different influence patterns of FC and EC modes on the valence state changes of the active sites of the air electrode, clarify the electrode attenuation mechanism under different operating modes, and provide a clear direction for targeted electrode optimization.

[0014] In a preferred embodiment, after testing in FC mode, the valence state of Co gradually increases from the electrode / electrolyte interface to the electrode surface in the air electrode; after testing in EC mode, the valence state of Co gradually decreases from the electrode / electrolyte interface to the electrode surface in the air electrode. This invention establishes a direct correspondence between FC and EC modes and the trend of Co valence state changes, revealing the electrode attenuation law under different operating modes from the perspective of valence state changes, and providing a specific technical basis for subsequently improving electrode stability by controlling the valence state of Co.

[0015] In a preferred embodiment, in step S2, the synchrotron radiation micro-area beamline test is an air electrode micro-area test, realizing the spatial gradient valence state characterization of active site elements along the thickness direction of the air electrode. This invention utilizes the spatial resolution capability of synchrotron radiation micro-area beamlines to achieve the characterization of the spatial gradient valence state along the thickness direction at the electrode micro-area scale, accurately capturing the attenuation characteristics of local electrode regions and revealing the microscopic mechanism of electrode attenuation in greater detail.

[0016] The characterization method of this invention achieves micro-area testing of the K-edge near-edge absorption spectrum of active site elements by dividing the air electrode into gradient sites and combining it with the high spatial resolution of synchrotron radiation micro-area beamlines. Based on the comparison of absorption spectrum characteristics, it quantitatively determines the valence state changes of active site elements. This method not only addresses the intrinsic fundamental factor of electrode decay—the valence state change of active site elements—but also overcomes the limitation of existing technologies that can only obtain apparent information about the electrode. Furthermore, it accurately captures the valence state gradient change pattern along the thickness direction of the air electrode, clearly distinguishing the influence mechanism and decay pattern of different operating modes such as power generation and electrolysis on the air electrode. This enables precise characterization of the decay degree of the air electrode in solid oxide fuel cells / electrolytes, clearly defining the influence of different operating conditions on the electrode. It provides direct and effective theoretical basis and technical support for the material optimization and structural design of the air electrode, significantly improving the accuracy, relevance, and practicality of electrode decay characterization. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the solid oxide fuel cell / electrolyte in this invention and a schematic diagram of the distribution of test sites on the cross-section of the air electrode.

[0018] Figure 2 The air electrode in Embodiment 1 of this invention uses the ABO3 type monoperovskite material Ba. 0.5 Sr 0.5 Co 0.8 Fe 0.2 X-ray diffraction (XRD) test results of O3 (BSCF) powder.

[0019] Figure 3 This is a comparison of the K-edge near-edge absorption spectra of Co element at test sites P1 to P4 on the cross-section of the electrode before reaction after BSCF powder is used to make an air electrode in Example 1 of the present invention, and a detailed comparison of the absorption spectra at each point in the range of jump 0.7 to 0.9. The left side shows the full spectrum comparison trend of the near-edge absorption spectrum, and the right side shows the local magnified comparison at the jump 0.7 to 0.9.

[0020] Figure 4 This is a comparison of the K-side near-side absorption spectra of Co element at test sites P1 to P4 on the cross-section of the electrode after the BSCF powder was made into an air electrode and tested in the power generation (FC) mode in Example 1 of the present invention. It also shows a detailed comparison of the absorption spectra at each point in the range of 0.7 to 0.9. The left side shows the overall spectrum comparison trend, and the right side shows the local magnified comparison at the jump of 0.7 to 0.9.

[0021] Figure 5This is a comparison of the K-side near-side absorption spectra of Co element at test sites P1 to P4 on the cross-section of the electrode after the BSCF powder was made into an air electrode in Example 1 of the present invention and tested in electrolysis (EC) mode. It also shows a detailed comparison of the absorption spectra at each point in the range of 0.7 to 0.9. The left side shows the overall spectrum comparison trend, and the right side shows the local magnified comparison at the jump of 0.7 to 0.9.

[0022] Figure 6 The air electrode in Embodiment 2 of this invention uses the AA′B2O6 type double perovskite structure material PrBa 0.8 Ca 0.2 X-ray diffraction (XRD) test results of CoO6 (PBCC) powder.

[0023] Figure 7 This is a comparison of the K-side near-side absorption spectra of Co element at test sites P1 to P4 on the cross-section of the electrode before reaction after PBCC powder is used to make an air electrode in Example 2 of the present invention, and a detailed comparison of the absorption spectra at each point in the range of jump 0.7 to 0.9. The left side shows the overall spectrum comparison trend, and the right side shows the local magnified comparison at the jump 0.7 to 0.9.

[0024] Figure 8 This is a comparison of the K-side near-side absorption spectra of Co element at test sites P1 to P4 on the cross-section of the electrode after the PBCC powder was made into an air electrode and tested in the power generation (FC) mode in Example 2 of the present invention. It also shows a detailed comparison of the absorption spectra at each point in the range of 0.7 to 0.9. The left side shows the overall spectrum comparison trend, and the right side shows the local magnified comparison at the jump of 0.7 to 0.9.

[0025] Figure 9 This is a comparison of the K-side near-side absorption spectra of Co element at test sites P1 to P4 on the cross-section of the electrode after the PBCC powder was made into an air electrode in Example 2 of the present invention and tested in electrolysis (EC) mode. It also shows a detailed comparison of the absorption spectra at each point in the range of 0.7 to 0.9. The left side shows the overall spectrum comparison trend, and the right side shows the local magnified comparison at the jump of 0.7 to 0.9. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1As shown, the solid oxide fuel cell / electrolyte of the present invention includes a dense electrolyte located between an air electrode and a fuel electrode. Four test sites, P1, P2, P3, and P4, are uniformly arranged sequentially from the electrode / electrolyte interface to the electrode surface along the thickness direction of the air electrode. These sites are used to accurately test the valence state of active site elements at different depths of the air electrode. Specifically, P1 is the test site closest to the electrode / electrolyte interface and farthest from the electrode surface, P4 is the test site farthest from the electrode / electrolyte interface and closest to the electrode surface, and P2 and P3 are intermediate test sites uniformly distributed along the thickness direction of the air electrode between P1 and P4.

[0028] The characterization method provided by this invention is applicable to characterizing the changes in the valence state of active site elements in the air electrode of a solid oxide fuel cell (SOFC) / solid oxide electrolyzer (SOEC) before and after operation in power generation (FC) and electrolysis (EC) modes, respectively, thereby determining the degree of degradation of the air electrode. First, the cross-section of the air electrode is divided into four test sites, P1 to P4, from the electrode / electrolyte interface to the electrode surface. Then, a synchrotron radiation micro-area beamline with spatial resolution is used to collect the near-edge absorption spectra of active site elements at each test site. Finally, by comparing the absorption spectrum characteristics under different operating conditions, the law of valence state change of active site elements is determined, thereby achieving accurate characterization of electrode degradation.

[0029] Among them, the electrochemical reaction occurring at site P1 was the most intense, and the electrode was most affected; the electrochemical reaction occurring at site P4 was the weakest, and the electrode was least affected; the air electrode was a Co-based perovskite, and Ba, an ABO3 type monoperovskite material containing Co at the B site, was selected. 0.5 Sr 0.5 Co 0.8 Fe 0.2 O3 (BSCF) or AA′B2O6 type double perovskite structural material PrBa 0.8 Ca 0.2For CoO6 (PBCC), the active site element tested was Co, which plays a major catalytic role. The collected absorption spectrum was the K-edge near-edge absorption spectrum of Co. This invention selects the K-edge near-edge absorption spectrum of Co in an air electrode as the characterization basis. The core reason is that in transition metals, Co, as a catalytic active site, has much higher electrochemical activity than other elements. Therefore, in ABO3 type single perovskite materials or AA′B2O6 type double perovskite structures, materials containing Co at the B site have better catalytic performance. The K-edge near-edge absorption spectrum of Co is highly sensitive to changes in its chemical valence state, and within the normalized absorption intensity range of 0.7~0.9, the valence state of Co and the energy shift of the near-edge absorption spectrum show a clear and stable linear positive correlation. Specifically, when the valence state of Co increases, the binding force of the atomic nucleus to the outer electrons strengthens, the energy required for electron ionization increases, and the energy position of the near-edge absorption spectrum shifts towards higher energy (right side). When the valence state decreases, it shifts towards lower energy (left side). Specifically, the normalized absorption intensity range of 0.7 to 0.9 is the core observation window for Co valence state analysis. It has the highest sensitivity and strongest anti-interference ability for the valence state changes of Co from +2 to +4 during the operation of the air electrode, enabling precise quantitative comparison of micro-area test results. This invention is the first to combine this linear characteristic with the spatial site division of the air electrode P1-P4 and the operating characteristics of the FC / EC dual mode, realizing the spatial gradient characterization of the Co valence state in the thickness direction of the air electrode, and the comparative analysis of the electrode valence state change law under the FC / EC dual mode, thereby accurately characterizing the attenuation degree of the air electrode and the influence mechanism of different operating conditions.

[0030] Example 1

[0031] In this embodiment, ABO3 type single perovskite material BSCF is selected as the air electrode material for solid oxide fuel cell / electrolyte. The characterization method of this invention is used to characterize the air electrode before reaction, after FC mode test, and after EC mode test. Specifically, the K-side near-edge absorption spectrum of Co element at test sites P1 to P4 of the electrode cross section is measured. By comparing the absorption spectrum characteristics of different sites and different reaction conditions, the valence state change of Co element is determined, thereby characterizing the degree of attenuation of the air electrode.

[0032] Figure 2 The figure shows the XRD test results of the BSCF powder in Example 1. It can be clearly seen from the figure that the prepared BSCF powder has a simple single perovskite structure and no other impurity phases appear.

[0033] Figure 3The figure shows a comparison of the K-side near-side spectra of Co at positions P1 to P4 before the reaction, and a detailed comparison of the corresponding jumps at 0.7 to 0.9, after the BSCF powder was used to make the electrode in Example 1. As can be clearly seen from the figure, the four spectra from P1 to P4 are basically overlapping, especially at the jumps of 0.7 to 0.9, without any tendency to shift to the left or right. This indicates that before the reaction, the valence state of Co at positions P1 to P4 of the air electrode is basically the same. From the electrode / electrolyte interface to the electrode surface, there is no phase separation or segregation of the electrode material, and the initial state of the electrode is uniform.

[0034] Figure 4 The figure shows the comparison of the K-side near-side spectra of Co element at positions P1 to P4 after the BSCF powder was used to make the electrode in Example 1, and the detailed comparison of the corresponding jumps at 0.7 to 0.9. It can be clearly seen from the figure that there are obvious fluctuations in the four spectra from P1 to P4, especially at the jumps of 0.7 to 0.9. The absorption spectrum position is obviously shifted to the right from P1 to P4, and the spectrum position at P4 is closer to that before the reaction. This indicates that after the FC mode test, the valence state of Co element at position P1 of the air electrode is significantly lower than that at position P4. From the electrode / electrolyte interface to the electrode surface, the valence state of Co element shows a gradual increasing trend.

[0035] The reason for this change in valence state is as follows: In FC mode, an oxygen reduction reaction occurs at the air electrode. During this process, Co, as the core catalytic center of the air electrode, participates in electron transfer. An oxygen molecule undergoes a reduction reaction at the catalytic site, requiring four electrons transferred from the external circuit to Co to generate two oxygen ions. These oxygen ions are then transferred to the fuel electrode via the electrolyte, where they react with hydrogen to generate two water molecules and four electrons, forming a closed loop. This electrochemical reaction occurs most intensely at the electrode / electrolyte interface. The closer to the electrode / electrolyte interface, the higher the degree of reduction. Therefore, after testing in FC mode, the closer the electrode region is to the electrode / electrolyte interface, the more electrons Co loses, the more significant the reduction, and the lower the valence state.

[0036] Figure 5 The figure shows the comparison of the K-side near-side spectra of Co at positions P1 to P4 after EC mode testing of the BSCF powder electrode in Example 1, and the detailed comparison of the corresponding jumps at 0.7 to 0.9. It can be clearly seen from the figure that there are obvious fluctuations in the four spectra from P1 to P4, especially at the jumps of 0.7 to 0.9. The absorption spectrum position shifts significantly to the left from P1 to P4, and the spectrum position at P4 is closer to that before the reaction. This indicates that after EC mode testing, the valence state of Co at position P1 of the air electrode is significantly higher than that at position P4. From the electrode / electrolyte interface to the electrode surface, the valence state of Co gradually decreases.

[0037] The reason for this change in valence state is as follows: In EC mode, an oxygen generation reaction occurs at the air electrode. During this process, Co, as the core catalytic center of the air electrode, participates in electron transfer. Two water molecules are decomposed at the fuel electrode to generate hydrogen ions and oxygen ions. The hydrogen ions combine to form hydrogen molecules at the fuel electrode and are released. The two oxygen ions are transferred from the electrolyte to the Co catalytic site of the air electrode. The oxygen ions lose electrons, are oxidized, and combine to form an oxygen molecule. The four electrons released are first transferred to the Co element, and then transferred to the fuel electrode via the Co element to the external circuit, forming a closed loop. This electrochemical reaction occurs most strongly at the electrode / electrolyte interface. The closer to the electrode / electrolyte interface, the higher the degree of oxidation. Therefore, after EC mode testing, the closer the electrode region is to the electrode / electrolyte interface, the more electrons Co gains, the more obvious the degree of oxidation, and the higher the valence state.

[0038] Example 2

[0039] In this embodiment, AA′B2O6 type double perovskite structure material PBCC is selected as the air electrode material of solid oxide fuel cell / electrolyte. The same characterization method as in Example 1 is used to characterize the air electrode before reaction, after FC mode test, and after EC mode test. The K-side near-edge absorption spectrum of Co element at test sites P1 to P4 of the electrode cross section is measured. By comparing the absorption spectrum characteristics of different sites and under different operating conditions, the valence state change of Co element is determined, and the degree of attenuation of air electrode is characterized.

[0040] Figure 6 The figure shows the XRD test results of PBCC powder in Example 2. It can be clearly seen from the figure that the prepared PBCC powder has a simple perovskite structure and no other impurity phases appear.

[0041] Figure 7 , Figure 8 and Figure 9 The figures above show the comparison of the K-edge near-edge spectra of Co element at P1 to P4 after the PBCC powder was used to make the electrode in Example 2, before the reaction, after the FC mode test, and after the EC mode test, as well as the detailed comparison results at the corresponding jump heights of 0.7 to 0.9. As can be clearly seen from the above figures, this example obtained the exact same test results as Example 1.

[0042] Before the reaction, the four spectra from P1 to P4 were basically overlapping, especially at the jump height of 0.7 to 0.9, and there was no tendency to shift to the left or right. This indicates that the valence state of Co at the P1 to P4 sites of the air electrode was basically the same before the reaction. From the electrode / electrolyte interface to the electrode surface, there was no phenomenon of Co layering or segregation, and the initial state of the electrode was uniform.

[0043] After the FC mode test, the four spectra from P1 to P4 showed obvious fluctuations. The absorption spectrum positions at jumps of 0.7 to 0.9 were significantly shifted to the right from P1 to P4, and the spectrum position at the P4 site was closer to that before the reaction. This indicates that after the FC mode test, the valence state of Co at the P1 site of the air electrode was significantly lower than that at the P4 site. From the electrode / electrolyte interface to the electrode surface, the valence state of Co gradually increased.

[0044] After EC mode testing, the four spectra from P1 to P4 showed significant fluctuations. The absorption spectrum positions at jumps of 0.7 to 0.9 were significantly shifted to the left from P1 to P4, and the spectrum position at P4 was closer to that before the reaction. This indicates that after EC mode testing, the valence state of Co at the P1 site of the air electrode was significantly higher than that at the P4 site. From the electrode / electrolyte interface to the electrode surface, the valence state of Co gradually decreased.

[0045] In summary, the characterization method of this invention can effectively characterize the valence state changes of two commonly used air electrode materials, BSCF and PBCC, under different operating modes of FC and EC, accurately reflecting the attenuation degree of the air electrode and the influence mechanism of different operating conditions on the electrode, and can provide a clear direction for subsequent electrode material optimization and structural design.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for characterizing an air electrode in a solid oxide fuel cell / electrolyte, characterized in that, To characterize the valence state changes of active site elements in the air electrode of a solid oxide fuel cell / solid oxide electrolyzer before and after operation in power generation and electrolysis modes, respectively, the method includes the following steps: S1, the cross-section of the air electrode is divided into multiple test sites from the electrode / electrolyte interface to the electrode surface; S2, using a synchrotron radiation micro-area beamline with spatial resolution, collect the K-side near-side absorption spectra of active site elements at each test site of the air electrode. S3. By comparing the K-edge near-edge absorption spectrum characteristics of each test site under different operating conditions, the valence state changes of the active site elements are determined, thereby determining the degree of attenuation of the air electrode.

2. The characterization method according to claim 1, characterized in that, In step S1, the test sites are arranged sequentially from the electrode / electrolyte interface to the electrode surface along the thickness direction of the air electrode, including a first test site close to the electrode / electrolyte interface, a fourth test site close to the electrode surface, and at least one intermediate test site located between the first test site and the fourth test site; wherein, the first test site is the site closest to the electrode / electrolyte interface and farthest from the electrode surface, and the fourth test site is the site farthest from the electrode / electrolyte interface and closest to the electrode surface.

3. The characterization method according to claim 2, characterized in that, In step S1, four test sites are set, namely P1, P2, P3 and P4, P1 is the first test site, P4 is the fourth test site, and P2 and P3 are the intermediate test sites and are evenly distributed along the thickness direction of the air electrode.

4. The characterization method according to claim 1, characterized in that, The air electrode is a Co-based perovskite material, the active site element is Co, and the Co-based perovskite material is an ABO3 type single perovskite material containing Co at the B site or an AA′B2O6 type double perovskite structure material.

5. The characterization method according to claim 4, characterized in that, The ABO3 type single perovskite material is BSCF, and the AA′B2O6 type double perovskite structure material is PBCC.

6. The characterization method according to claim 1, characterized in that, In step S3, the valence state change of the active site element is determined by comparing the energy shift of the K-side near-side absorption spectrum within the normalized absorption intensity range of 0.7 to 0.

9. The valence state of the active site element is linearly positively correlated with the energy shift of the absorption spectrum within this range. When the valence state of the element increases, the energy position of the absorption spectrum shifts towards higher energy, and when the valence state of the element decreases, the energy position of the absorption spectrum shifts towards lower energy.

7. The characterization method according to claim 6, characterized in that, The normalized absorption intensity range of 0.7 to 0.9 is the core observation window for the valence state analysis of Co, and is suitable for testing the valence state changes of Co from +2 to +4.

8. The characterization method according to claim 1, characterized in that, In step S3, the different operating conditions include before the reaction, after the power generation mode test, and after the electrolysis mode test; by comparing the K-side near-side absorption spectrum characteristics of each test site under the three operating conditions, the influence of the power generation mode and the electrolysis mode on the air electrode is determined.

9. The characterization method according to claim 8, characterized in that, After the power generation mode test, the valence state of Co in the air electrode gradually increased from the electrode / electrolyte interface to the electrode surface; after the electrolysis mode test, the valence state of Co in the air electrode gradually decreased from the electrode / electrolyte interface to the electrode surface.

10. The characterization method according to claim 1, characterized in that, In step S2, the test of the synchrotron radiation micro-area beamline is an air electrode micro-area test, which realizes the spatial gradient valence state characterization of active site elements in the thickness direction of the air electrode.

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