Preparation and application of intermediate-temperature solid oxide fuel cell cathode material for improving Sm < 0.5 > Sr < 0.5 > FeO < 3-delta > oxygen reduction activity through B-site regulation

Abstract

The invention discloses preparation and application of a medium-temperature solid oxide fuel cell cathode material for improving Sm < 0.5 > Sr < 0.5 > FeO < 3-delta > oxygen reduction activity through B-site regulation and control, and belongs to the technical field of medium-temperature solid oxide fuel cells. According to the invention, the Sm < 0.5 > Sr < 0.5 > Fe < 1-x > Ni < x > O < 3-delta > series material is successfully synthesized by adopting an EDTA-citric acid sol-gel method. XRD (X-ray diffraction) results show that all samples are of cubic perovskite structures, and lattice shrinkage caused by Ni doping shows that Fe is successfully substituted to enter lattice sites. The uniformity of element distribution is further verified through HR-TEM (high-resolution transmission electron microscope) and EDS (energy spectrum element distribution) analysis.

Description

Technical Field

[0001] This invention belongs to the field of intermediate-temperature solid oxide fuel cell technology, and specifically relates to a method for improving Sm by B-site regulation. 0.5 S r0.5 FeO 3-δ Preparation and application of oxygen reduction-active intermediate-temperature solid oxide fuel cell cathode materials. Background Technology

[0002] Among numerous energy conversion technologies, solid oxide fuel cells (SOFCs) are considered one of the most promising clean energy technologies due to their advantages such as high energy conversion efficiency, low pollution emissions, and fuel versatility. However, traditional SOFCs require operation at high temperatures of 800-1000℃, which not only increases material costs but also places higher demands on the thermal matching and long-term stability of electrode and electrolyte materials, severely restricting their commercial application. Therefore, developing SOFCs capable of efficient operation in the intermediate temperature range (600-800℃) has become a core research direction.

[0003] Among numerous cathode materials, iron-based perovskite materials have attracted widespread attention due to their low cost, good high-temperature phase stability, and excellent thermal expansion matching with commonly used electrolytes (such as SDC and LSGM). However, these materials suffer from low oxygen reduction reaction activity. Studies have found that doping the B-site with the transition metal Ni can significantly improve electronic conductivity and oxygen ion transport performance. Ni has excellent electronic conductivity; doping with Ni promotes the adsorption and dissociation of oxygen molecules, increases the oxygen reduction reaction rate, and thus optimizes electrode polarization performance. For example, the La-based perovskite materials studied by Jin et al. 0.6 Ba 0.4 Fe 0.8 Ni 0.2 O 3-δ The material's conductivity was improved by Ni doping, but La 3+ The large ionic radius leads to significant lattice volume expansion, a high coefficient of thermal expansion, and poor thermal matching with the electrolyte.

[0004] Furthermore, patent CN115224285A discloses a medium-temperature solid oxide fuel cell cathode material, its preparation method, and its application. This technology uses a solid-state method to prepare Ni-doped cathode materials. Although this method has advantages such as simple process and low cost, the solid-state method suffers from problems such as uneven mixing and uneven element distribution in actual operation. In this technology, Ni doping mainly plays a role in enhancing electronic conductivity, but under high-temperature reducing atmosphere, Ni is prone to migration and aggregation, leading to reduced catalytic activity and structural stability, affecting the actual application performance of the material. Although existing technologies have made some progress in B-site Ni doping, there are still significant shortcomings in terms of thermal expansion control, uniform Ni distribution, and structural stability. Summary of the Invention

[0005] To overcome the shortcomings of existing IT-SOFC (intermediate-temperature solid oxide fuel cell) cathode materials in terms of oxygen reduction reaction activity, conductivity, and thermal expansion matching, this invention provides a method for improving Sm by B-site regulation. 0.5 S r0.5 FeO 3-δ The invention relates to the preparation and application of oxygen reduction-active intermediate-temperature solid oxide fuel cell cathode materials. By introducing an appropriate amount of Ni element doping into the B site of the perovskite structure, the conductivity and thermal expansion coefficient are synergistically regulated, thereby improving the electrochemical performance of the material under intermediate-temperature conditions.

[0006] A B-site regulation enhances Sm 0.5 Sr 0.5 FeO 3-δ Oxygen reduction active intermediate-temperature solid oxide fuel cell cathode material, with the chemical formula Sm 0.5 Sr 0.5 Fe 1-x NixO 3-δ , where 0 < x ≤ 0.1; δ is the oxygen vacancy concentration, 0.25 < δ ≤ 0.3.

[0007] Furthermore, x is 0.1.

[0008] One of the above-mentioned B-site regulation methods enhances Sm 0.5 Sr 0.5 FeO 3-δ A method for preparing oxygen reduction-active intermediate-temperature solid oxide fuel cell cathode material includes the following steps:

[0009] Sm(NO3)3, Sr(NO3)2, Fe(NO3)3·9H2O, and Ni(NO3)2·6H2O were dissolved in water to prepare mixed solution one. Ethylenediaminetetraacetic acid and citric acid were added to mixed solution one, and the pH was adjusted after dissolution to obtain mixed solution two. Mixed solution two was heated and continuously stirred until it reached a viscous state, then heat-treated and calcined to obtain the B-site-modified Sm... 0.5 Sr 0.5 FeO 3-δ Oxygen-reducing active intermediate-temperature solid oxide fuel cell cathode material.

[0010] Furthermore, the molar ratio of total metal ions, citric acid, and ethylenediaminetetraacetic acid in the mixed solution is (0.9-1.1):(0.9-1.1):(1.4-1.6).

[0011] Furthermore, the heating temperature is 80°C.

[0012] Furthermore, the calcination temperature is 1100℃ and the time is 5 hours.

[0013] Furthermore, the pH is 8.

[0014] One of the above-mentioned B-site regulation methods enhances Sm 0.5 Sr 0.5 FeO 3-δ Application of oxygen reduction-active intermediate-temperature solid oxide fuel cell cathode materials in the preparation of intermediate-temperature solid oxide fuel cells.

[0015] Furthermore, the electrolyte of the intermediate-temperature solid oxide fuel cell is Sm 0.2 Ce 0.8 O 2-δ The anode is NiO and Sm 0.2 Ce 0.8 O 2-δ Composite anode materials.

[0016] The technical principle of this invention is as follows: This invention uses 25wt.% ammonia water to adjust the pH instead of NaOH, thus avoiding the introduction of Na+. + Impurities are eliminated, and since ammonia is a weak alkali, the operation is relatively safer. These impurities can be removed during subsequent muffle furnace calcination, leaving no residue and ensuring product purity. This invention uses an 80℃ constant-temperature water bath for heating and stirring, ensuring uniform heating of the precursor system and reducing concentration gradients. Compared to direct heating, the water bath provides a stable heat source, avoiding localized overheating and promoting uniform component distribution.

[0017] Compared to the above-mentioned technologies, this invention provides a Sm 0.5 Sr 0.5 Fe 1-x NixO3-δ The cathode material, through equimolar Sm / Sr doping at the A-site, improves its thermal expansion matching with the electrolyte. An appropriate amount of Ni is introduced at the B-site, and through synergistic interaction with Fe, it regulates electron and ion transport pathways, enhancing oxygen reduction activity. Simultaneously, the sol-gel method is used to prepare the material, resulting in a more uniform elemental distribution and effectively avoiding Ni agglomeration at high temperatures. The prepared material has a small particle size, which is beneficial for oxygen molecule adsorption and dissociation, enhancing oxygen reduction activity. Furthermore, this invention verifies the uniform Ni doping in the material through EDS elemental distribution analysis, effectively ensuring the stability of the material structure and electrochemical performance. This fundamentally overcomes the elemental agglomeration and structural instability problems inherent in solid-state methods, exhibiting superior electrochemical performance of the mid-temperature SOFC cathode.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] This invention provides a method for B-site modulation to enhance Sm 0.5 Sr 0.5 FeO 3-δ An oxygen reduction-active intermediate-temperature solid oxide fuel cell cathode material, Sm, was successfully synthesized using the EDTA-citric acid sol-gel method. 0.5 Sr 0.5 Fe 1-x Ni x O 3-δ A series of materials were developed. XRD (X-ray diffraction) results showed that all samples exhibited a cubic perovskite structure, and the lattice contraction induced by Ni doping indicated that it successfully substituted Fe into lattice sites. HR-TEM (high-resolution transmission electron microscopy) and EDS (energy dispersive spectroscopy) analysis further verified the uniformity of elemental distribution. TEC (coefficient of thermal expansion) tests showed that the doped materials exhibited good thermal matching with the commonly used electrolyte SDC in the temperature range from room temperature to 750℃. Conductivity tests showed that Ni doping significantly improved electronic conductivity, with the sample with x=0.1 exhibiting a conductivity as high as 237.54 Scm at 800℃. -1 The polarization resistance was three times that of the undoped sample. Although electrochemical impedance spectroscopy (EIS) showed that Ni doping increased polarization resistance, its performance was still superior to some Co-based materials. Finally, single-cell tests based on NiO-SDC anode support showed that the doped sample achieved a peak power density (PPD) of 645.69 mW·cm⁻¹ at 800 °C. -2 It is significantly better than the undoped sample (285.18 mW·cm⁻¹). -2 Therefore, appropriate Ni doping is an effective strategy to improve the application performance of Fe-based perovskite materials. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 (a) shows the XRD patterns of the cathode materials prepared in Examples 1-4 and Comparative Example 1; (b) shows the magnified XRD patterns in the range of 32.0°≤2θ≤33.0°; (c) shows the Sm... 0.5 Sr 0.5 Fe 0.9 Ni 0.1 O 3-δ XRD pattern of the mixture with electrolyte SDC;

[0022] Figure 2 The images show Rietveld refinement images of the cathode materials prepared in Examples 1-4 and Comparative Example 1, where (a) represents SSF and (b) represents SSFN. 0.025 (c) is SSFN 0.05 (d) is SSFN 0.075 (e) is SSFN 0.1 ;

[0023] Figure 3 SSFN prepared in Example 1 0.1 HR-TEM image;

[0024] Figure 4 The elemental distribution (EDS) diagrams of SSFN0.1 prepared in Example 1 are shown, where (a) is a scanning transmission electron microscope (STEM) image of the sample, (b) is the elemental distribution diagram of Sm, (c) is the elemental distribution diagram of Sr, (d) is the elemental distribution diagram of Fe, (e) is the elemental distribution diagram of Ni, and (f) is the elemental distribution diagram of O.

[0025] Figure 5 (a), (b), (c), (d), and (e) in the figure represent SSF|SDC and SSFN, respectively. 0.025 |SDC、SSFN 0.05 |SDC、SSFN 0.075 |SDC、SSFN 0.1 SEM image of the cross section of SDC, (f) is SSFN 0.1 SEM image of the cross section of |SDC|NiO-SDC;

[0026] Figure 6 The thermal expansion curves of the cathode materials prepared in Examples 1-4 and Comparative Example 1 from room temperature to 750°C are shown.

[0027] Figure 7 The conductivity temperature variation graphs of the cathode materials prepared in Examples 1-4 and Comparative Example 1 at 250-800℃ are shown.

[0028] Figure 8 The electrochemical impedance spectroscopy and Bode plots of the symmetrical cells prepared in Example 1 were measured at 600-800 °C. Among them, (a), (b), (c), (d) and (e) are the electrochemical impedance spectroscopy of the symmetrical cells prepared with the cathode materials of Examples 1-4 and Comparative Example 1, respectively, and (f) is the Bode plot of the symmetrical cells prepared with the cathode materials of Examples 1-4 and Comparative Example 1 at 800 °C.

[0029] Figure 9 The graphs show the current density-voltage-power density (IVP) curves of the composite anode single cell prepared in Example 2, measured at 600-800 °C. In this graph, (a) represents SSF|SDC|NiO-SDC, and (b) represents SSFN. 0.1 |SDC|NiO-SDC. Detailed Implementation

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0032] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0033] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0034] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0035] This invention provides a method for B-site modulation to enhance Sm 0.5 Sr 0.5 FeO 3-δ A method for preparing oxygen reduction-active intermediate-temperature solid oxide fuel cell cathode material, the molecular formula of the prepared material being Sm 0.5 Sr 0.5 Fe 1-x NixO 3-δ Where 0 < x ≤ 0.1; δ is the oxygen vacancy concentration, 0.25 < δ ≤ 0.3, and it is synthesized by the EDTA-citric acid sol-gel method.

[0036] This invention also uses XRD, HR-TEM, and EDS tests to demonstrate that Ni was successfully doped into Fe sites, causing lattice contraction. Electrochemical performance tests show that the doped material exhibits excellent conductivity at intermediate temperatures (up to 237.54 S·cm). -1 And thermal expansion matching. Single-cell tests show that the doped sample can achieve 645.69 mW·cm⁻¹ at 800℃. -2 The peak power density is higher than that of the undoped sample (285.18 mW·cm⁻¹). -2 The improvement is significant. The preparation method provided by this invention is simple and efficient, and the obtained material has excellent electrochemical performance, making it suitable for the preparation and application of high-performance IT-SOFC cathodes.

[0037] The room temperature in this invention refers to 25±2℃.

[0038] The raw materials Sm(NO3)3, Sr(NO3)2, Fe(NO3)3·9H2O and Ni(NO3)2·6H2O used in the embodiments of the present invention are all analytical grade.

[0039] Example 1

[0040] A B-site regulation enhances Sm 0.5 Sr 0.5 FeO 3-δ A method for preparing an oxygen reduction-active intermediate-temperature solid oxide fuel cell cathode material, with the chemical formula Sm 0.5 Sr0.5 Fe 0.9 Ni 0.1 O 3-δ δ is set to 0.3, and the specific steps include:

[0041] S1. Weigh 4.9802g (11.2mmol) of Sm(NO3)3, 2.3713g (11.2mmol) of Sr(NO3)2, 8.1482g (20.2mmol) of Fe(NO3)3·9H2O and 0.6517g (2.24mmol) of Ni(NO3)2·6H2O, dissolve them in 150mL of deionized water to obtain mixed solution one;

[0042] S2. Add 19.6471 g (67.2 mmol) of ethylenediaminetetraacetic acid and 9.4184 g (49.0 mmol) of citric acid to mixed solution one, and continue stirring until completely dissolved. Then adjust the pH of the solution to 8 with 25 wt.% ammonia water to obtain mixed solution two.

[0043] S3. Mixed solution 2 is heated in a constant temperature water bath at 80℃ and stirred until it becomes viscous. Then it is heat-treated in an electric resistance furnace at 200℃ for 2 hours to prepare the precursor powder.

[0044] S4. The precursor powder was placed in a muffle furnace and calcined at 1100℃ for 5 hours to obtain Sm. 0.5 Sr 0.5 Fe 0.9 Ni 0.1 O 3-δ Cathode material, denoted as SSFN 0.1 .

[0045] Comparative Example 1

[0046] Same as Example 1, except that in S1, Ni(NO3)2·6H2O is replaced by Fe(NO3)3·9H2O in equal molar amounts. The specific operation includes the following steps:

[0047] S1. Weigh 4.9866g of Sm(NO3)3, 2.3743g of Sr(NO3)2, and 9.0651g of Fe(NO3)3·9H2O, dissolve them in 150mL of deionized water to obtain mixed solution one;

[0048] S2. Add 19.6722 g of ethylenediaminetetraacetic acid and 9.4304 g of citric acid to mixed solution one, stir continuously until completely dissolved, and then adjust the pH of the solution to 8 with 25 wt.% ammonia water to obtain mixed solution two;

[0049] S3-S4 are the same as in Example 1, and the cathode material prepared is denoted as SSF.

[0050] Example 2

[0051] Same as Example 1, except that 75 mol% Ni(NO3)2·6H2O is replaced with Fe(NO3)3·9H2O. The specific operation includes the following steps:

[0052] S1. Weigh 4.9850g of Sm(NO3)3, 2.3736g of Sr(NO3)2, 8.8357g of Fe(NO3)3·9H2O, and 0.1631g of Ni(NO3)2·6H2O, dissolve them in 150mL of deionized water to obtain mixed solution one;

[0053] S2. Add 19.6659 g of ethylenediaminetetraacetic acid and 9.4274 g of citric acid to mixed solution one, stir continuously until completely dissolved, and then adjust the pH of the solution to 8 with 25 wt.% ammonia water to obtain mixed solution two;

[0054] S3-S4 are the same as in Example 1, and the cathode material prepared is denoted as SSFN. 0.025 .

[0055] Example 3

[0056] Same as Example 1, except that 50 mol% Ni(NO3)2·6H2O is replaced with Fe(NO3)3·9H2O. The specific operation includes the following steps:

[0057] S1. Weigh 4.9834g of Sm(NO3)3, 2.3728g of Sr(NO3)2, 8.6063g of Fe(NO3)3·9H2O, and 0.3260g of Ni(NO3)2·6H2O, dissolve them in 150mL of deionized water to obtain mixed solution one;

[0058] S2. Add 19.6595g of ethylenediaminetetraacetic acid and 9.4243g of citric acid to mixed solution one, stir continuously until completely dissolved, and then adjust the pH of the solution to 8 with 25wt.% ammonia water to obtain mixed solution two;

[0059] S3-S4 are the same as in Example 1, and the cathode material prepared is denoted as SSFN. 0.05 .

[0060] Example 4

[0061] Same as Example 1, except that 25 mol% Ni(NO3)2·6H2O is replaced with Fe(NO3)3·9H2O. The specific operation includes the following steps:

[0062] S1. Weigh 4.9818g of Sm(NO3)3, 2.3720g of Sr(NO3)2, 8.3772g of Fe(NO3)3·9H2O, and 0.4889g of Ni(NO3)2·6H2O, dissolve them in 150mL of deionized water to obtain mixed solution one;

[0063] S2. Add 19.6534 g of ethylenediaminetetraacetic acid and 9.4214 g of citric acid to mixed solution one, and stir continuously until completely dissolved. Then adjust the pH of the solution to 8 with 25 wt.% ammonia water to obtain mixed solution two.

[0064] S3-S4 are the same as in Example 1, and the cathode material prepared is denoted as SSFN. 0.075 .

[0065] Application Example 1

[0066] This application example provides a method for fabricating a symmetrical battery, using the SSFN cathode material prepared in Example 1 as the cathode. 0.1 SSF prepared in Comparative Example 1 and SSFN prepared in Example 2 0.025 SSFN prepared in Example 3 0.05 SSFN prepared in Example 4 0.075 The electrolyte is SDC, and a symmetrical cathode|electrolyte|cathode structure is adopted, specifically including the following steps:

[0067] S1. Weigh 0.4g of SDC and place it into a circular mold with a diameter of 15mm. Press it into a sheet under a pressure of 10MPa for 2min. Calcination is carried out using a double Al2O3 plate. Place the pressed SDC sheet in the middle and calcine it in a muffle furnace at 1450℃ for 5h to obtain electrolyte sheets.

[0068] S2. Weigh 1g of the above cathode material, 0.94g of terpineol and 0.06g of ethyl cellulose respectively, place them in a mortar and grind them evenly to obtain cathode slurry;

[0069] S3. The cathode paste from step S2 is coated onto the electrolyte sheet from step S1 using screen printing technology, and then calcined in a muffle furnace at 1000°C for 2 hours to obtain a symmetrical cell (the cathode in the cathode paste is SSFN). 0.1 At that time, the symmetrical cell was marked as SSFN. 0.1 |SDC|SSFN 0.1 When the cathode in the cathode paste is SSF, the symmetrical cell is labeled as SSF|SDC|SSF; when the cathode in the cathode paste is SSFN... 0.025 At that time, the symmetrical cell was marked as SSFN. 0.025 |SDC|SSFN 0.025 The cathode in the cathode slurry is SSFN. 0.05At that time, the symmetrical cell was marked as SSFN. 0.05 |SDC|SSFN 0.05 The cathode in the cathode slurry is SSFN. 0.075 At that time, the symmetrical cell was marked as SSFN. 0.075 |SDC|SSFN 0.075 ).

[0070] Application Example 2

[0071] This application example provides a method for preparing a composite anode single cell, which specifically includes the following steps.

[0072] S1. Weigh 6g NiO, 4g SDC and 2.5g corn starch, place them in a ball mill jar, add an appropriate amount of anhydrous ethanol, and ball mill for 48h. After ball milling, dry in an oven at 100℃ for 48h to obtain composite anode material NiO-SDC.

[0073] S2. Weigh 0.3g of the composite anode from step S1, spread it evenly in a 15mm circular mold, add 0.04g of electrolyte SDC, and press it at 10MPa pressure for 2min to obtain a composite anode single cell.

[0074] S3. Weigh out 1g of the cathode material SSFN prepared in Example 1. 0.1 The SSF of Comparative Example 1 was thoroughly ground with 0.94 g of terpineol and 0.06 g of ethyl cellulose in a mortar to prepare a uniform cathode slurry.

[0075] S4. Using a screen printing process, the cathode paste from step S3 is coated onto the electrolyte surface of the single cell from step S2. The cell is then calcined in a muffle furnace at 1000°C for 2 hours to obtain an anode-supported single cell. Depending on the cathode material, the resulting single cells are labeled as follows: the cathode in the cathode paste is SSFN from Example 1. 0.1 At that time, a single cell was marked as SSFN. 0.1 |SDC|NiO-SDC; When the cathode in the cathode slurry is SSF (Comparative Example 1), the single cell is labeled as SSF|SDC|NiO-SDC.

[0076] Characterization results

[0077] 1. X-ray diffraction (XRD) characterization

[0078] Figure 1 (a) shows the XRD patterns of the cathode materials prepared in Examples 1-4 and Comparative Example 1; (b) shows the magnified XRD patterns in the range of 32.0°≤2θ≤33.0°; (c) shows the Sm... 0.5 Sr 0.5 Fe 0.9 Ni 0.1 O3-δ XRD pattern of the mixture with electrolyte SDC.

[0079] Figure 1 (a) shows Sm 0.5 Sr 0.5 Fe 1-x Ni x O 3-δ The XRD patterns of all samples showed a cubic perovskite structure with space group Pm-3m(211), and no impurity peaks were detected. With increasing Ni doping concentration, the diffraction peaks gradually shifted towards larger angles (e.g., ...). Figure 1 As shown in (b), this indicates lattice shrinkage after Ni doping. This phenomenon may be attributed to a charge compensation mechanism. (Low-valence) Partial replacement It can induce its oxidation into ions with smaller ionic radii. This ultimately leads to lattice contraction. Figure 1 In (c), only peaks of the perovskite structure of the cathode and the fluorite structure of the electrolyte were observed, indicating that there were no chemical reactions that led to the formation of the new phase, thus demonstrating excellent chemical compatibility.

[0080] 2. Rietveld Refined Characterization

[0081] To obtain the crystal size, the XRD pattern was further analyzed using the Rietveld refinement method. Figure 2 The images show Rietveld refinement images of the cathode materials prepared in Examples 1-4 and Comparative Example 1, where (a) represents SSF and (b) represents SSFN. 0.025 (c) is SSFN 0.05 (d) is SSFN 0.075 (e) is SSFN 0.1 .from Figure 2 As can be seen from this, with the increase of Ni doping amount, the lattice volume changes from... Reduce to The lattice volume gradually decreases, consistent with the diffraction peak shift pattern.

[0082] 3. Characterization by high-resolution transmission electron microscopy (HR-TEM)

[0083] Figure 3 SSFN prepared in Example 1 0.1 The HR-TEM image shows that the 0.2091 nm lattice spacing corresponds to the (111) crystal plane in the XRD, which is consistent with the XRD offset pattern.

[0084] Figure 4 SSFN prepared in Example 1 0.1The elemental distribution (EDS) diagrams are shown, where (a) is a scanning transmission electron microscope (STEM) image of the sample, (b) is the elemental distribution diagram of Sm, (c) is the elemental distribution diagram of Sr, (d) is the elemental distribution diagram of Fe, (e) is the elemental distribution diagram of Ni, and (f) is the elemental distribution diagram of O. Figure 4 The results show that all elements are evenly distributed, which also proves that Ni has been successfully doped into Sm. 0.5 Sr 0.5 Fe 1-x Ni x O 3-δ In this way, the cubic perovskite structure remains unchanged.

[0085] 4. Characterization by scanning electron microscopy (SEM)

[0086] Figure 5 (a), (b), (c), (d), and (e) in the figure represent SSF|SDC and SSFN, respectively. 0.025 |SDC、SSFN 0.05 |SDC、SSFN 0.075 |SDC、SSFN 0.1 SEM image of the cross section of SDC, (f) is SSFN 0.1 SEM image of the cross-section of |SDC|NiO-SDC. The image shows that the SDC electrolyte exhibits a dense and uniform microstructure. It is clearly visible that a tight bond is formed between the porous cathode material and the dense electrolyte, which facilitates the migration and diffusion of oxygen ions, thereby improving the ORR activity of the cathode. Furthermore, no obvious breakage or delamination was found between the electrode and the electrolyte, indicating good thermal matching and adhesion, effectively avoiding the influence of polarization impedance caused by interfacial contact.

[0087] 5. Characterization of thermal expansion

[0088] Figure 6 The thermal expansion curves of the cathode materials prepared in Examples 1-4 and Comparative Example 1 at room temperature to 750°C are shown.

[0089] The coefficient of thermal expansion directly affects the mechanical compatibility between the cathode material and the electrolyte at high operating temperatures. This compatibility plays a crucial role in the long-term stable operation and performance maintenance of SOFC devices. The thermal expansion behavior of perovskite oxides is usually closely related to the reduction of B-site transition metal ions. 0.5 Sr 0.5 Fe 1-x Ni x O 3-δ The increase in TEC in the sample can be attributed to defect structure changes induced by doping, which is closely related to Ni doping. The introduction of Ni and the increase in temperature promote the formation of oxygen vacancies, thereby inducing Fe...4+ Reduced to Fe 3+ And this is accompanied by the release of oxygen. Because Fe 3+ The ionic radius (0.645 μm) is greater than that of Fe. 4+ The ionic radius (0.585 μm) of FeO6 leads to octahedral expansion, which in turn induces lattice volume expansion. Simultaneously, it interacts with Fe... 4+ In comparison, Fe 3+ Its lower electronegativity weakens the Fe-O bond strength, thereby further enhancing the lattice expansion effect and increasing the TEC. Sm 0.5 Sr 0.5 Fe 1-x Ni x O 3-δ The TEC of the samples ranged from 14.37 to 14.81 × 10⁻⁶. -6 K -1 Compared with commonly used electrolytes, SDC (12.6 × 10⁻⁶) -6 K -1 It has good thermal compatibility.

[0090] 6. Conductivity Characterization

[0091] Figure 7 The graph shows the temperature variation of conductivity of the cathode materials prepared in Examples 1-4 and Comparative Example 1 at 250-800°C.

[0092] Electrical conductivity is one of the important indicators for evaluating the electrochemical performance of electrode materials. Total conductivity is composed of both electronic conductivity and ionic conductivity. Since the mobility of oxygen ions is much lower than that of electrons, electronic conductivity is usually the main contributor to total conductivity. Figure 7 The conductivity curves of the samples from 250 to 800 °C are shown, and all samples exhibit a similar temperature-dependent trend. When Sm 0.5 Sr 0.5 Fe 1-x Ni x O 3-δ The B-site cation in the middle is affected by divalent Ni 2+ During substitution, to maintain electroneutrality, the introduced effective negative charge needs to be balanced through electronic or ionic compensation mechanisms. This compensation can be achieved by increasing the valence state of the B-site cation (Fe). 3+ Oxidized to Fe 4+ This can be achieved either by generating oxygen vacancies. As shown in equation (1), in the reaction... and They represent Fe 3+ and Fe 4+ ; and These represent O ions and oxygen vacancies present in the crystal lattice, respectively.

[0093]

[0094] Within a temperature range below 350℃, the sample conductivity increases with increasing temperature, exhibiting typical semiconductor characteristics. At this temperature, electron compensation dominates, and charge carriers pass through Fe... 3+ and Fe 4+ Conduction is achieved through electronic transitions between them. As temperature increases, the small polarons (Fe...) 3+ -O-Fe 4+ The migration rate of Fe increases, thereby improving conductivity. However, as the temperature rises further, the conductivity begins to decrease with increasing temperature, exhibiting metallic-like properties. This shift indicates that the ion compensation mechanism is gradually becoming dominant. At high temperatures, lattice oxygen escapes, and the oxygen vacancy concentration increases accordingly. At this time, the reaction equilibrium in equation (1) shifts to the right, and this process reduces the concentration of high-valence B-site ions (Fe). 4+ The concentration of Ni disrupts the Fe-O-Fe electronic transition path, inhibiting effective charge migration within this channel and ultimately leading to a decrease in conductivity. As the Ni doping concentration increases, the conductivity also increases, with the highest conductivity of 237.54 S·cm at a Ni doping concentration of 0.1%. -1 It is approximately three times that of the undoped sample (76.81 S·cm). -1 ).

[0095] 7. Electrochemical impedance characterization

[0096] Figure 8 The electrochemical impedance spectroscopy (EIS) and Bode plots of the symmetrical cells prepared in Example 1 were measured at 600-800 °C. Among them, (a), (b), (c), (d), and (e) are the EIS of the symmetrical cells prepared with the cathode materials of Examples 1-4 and Comparative Example 1, respectively, and (f) is the Bode plot of the symmetrical cells prepared with the cathode materials of Examples 1-4 and Comparative Example 1 at 800 °C.

[0097] To more comprehensively evaluate the impact of Ni doping on the electrocatalytic activity of cathode materials Figure 8 SSFN was demonstrated x Electrochemical impedance spectroscopy (EIS) of symmetrical cells at 600-800℃. The equivalent circuit model adopts a Rohm-(RHF / / CPEHF)-(RLF / / CPELF) structure, where Rohm is the total ohmic resistance, and R and CPE represent the polarization resistance and constant phase element in different frequency ranges, respectively. For ease of explanation, Rohm caused by the SDC electrolyte and wires is omitted. The total polarization resistance (Rp) consists of RHF in the high-frequency region and RLF in the low-frequency region. Figure 8As shown in (a)-(e), the Rp of the symmetrical cell decreases significantly with increasing test temperature, indicating that the reaction kinetics at the electrode interface are enhanced. At 800℃, the Rp of the SSF is 0.124 Ω·cm. 2 SSFN 0.1 Rp is 0.201 Ω·cm 2 Although Ni doping increases Rp, it is still lower than that of some common Co-based materials. The corresponding peak range of the Bode curve is as follows: Figure 8 In (f), it was confirmed that Rp is mainly distributed in the high-frequency region, and the ORR kinetics are mainly limited by the electrochemical kinetics in the high-frequency region.

[0098] 8. Power density characterization

[0099] Figure 9 The graphs show the current density-voltage-power density (IVP) curves of the composite anode single cell prepared in Example 2, measured at 600-800 °C. In this graph, (a) represents SSF|SDC|NiO-SDC, and (b) represents SSFN. 0.1 |SDC|NiO-SDC.

[0100] In order to evaluate SSFN x Electrochemical performance of cathode materials in actual operation, using a NiO-SDC composite structure anode-supported single cell, SSFN x The peak power density (PPD) of the |SDC| NiO-SDC (x=0, 0.1) single cell was tested in the temperature range of 600-800℃. The anode side was supplied with 3% humidified H2, while the cathode side was exposed to ambient air as an oxidant. This is due to the Ce content in the SDC electrolyte. 4+ The ions are reduced to Ce under reducing and high temperature conditions. 3+ This results in n-type electronic conductivity. The presence of electrons in the electrolyte generates an internal short-circuit current, therefore the open-circuit voltage (OCV) of a single cell is lower than the theoretical voltage range of 1.04-1.1V. Figure 9 As shown, compared with undoped SSF|SDC|NiO-SDC (285.18 mW·cm⁻¹), -2 When Ni is doped by 0.1%, the PPD reaches 645.69 mW·cm⁻¹ at 800℃. -2 Compared to the undoped matrix, PPD was significantly improved.

[0101] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of B-site regulation to enhance Sm 0.5 Sr 0.5 FeO 3-δ Oxygen-reducing active intermediate-temperature solid oxide fuel cell cathode material, characterized in that, The chemical formula is Sm 0.5 Sr 0.5 Fe 1-x Ni x O 3-δ , where 0 < x ≤ 0.1; δ is the oxygen vacancy concentration, 0.25 < δ ≤ 0.

3.

2. The B-position regulation to improve Sm according to claim 1 0.5 Sr 0.5 FeO 3-δ Oxygen-reducing active intermediate-temperature solid oxide fuel cell cathode material, characterized in that, The value of x is 0.

1.

3. A method for enhancing Sm by B-site modulation as described in claim 1 or 2 0.5 Sr 0.5 FeO 3-δ A method for preparing oxygen-reducing active intermediate-temperature solid oxide fuel cell cathode material, characterized in that, Includes the following steps: Sm(NO3)3, Sr(NO3)2, Fe(NO3)3·9H2O, and Ni(NO3)2·6H2O were dissolved in water to prepare mixed solution one. Ethylenediaminetetraacetic acid and citric acid were added to mixed solution one, and the pH was adjusted after dissolution to obtain mixed solution two. Mixed solution two was heated and continuously stirred until it reached a viscous state, then heat-treated and calcined to obtain the B-site-modified Sm... 0.5 Sr 0.5 FeO 3-δ Oxygen-reducing active intermediate-temperature solid oxide fuel cell cathode material.

4. The preparation method according to claim 3, characterized in that, The molar ratio of total metal ions, citric acid, and ethylenediaminetetraacetic acid in the mixed solution is (0.9-1.1):(0.9-1.1):(1.4-1.6).

5. The preparation method according to claim 3, characterized in that, The heating temperature is 80°C.

6. The preparation method according to claim 3, characterized in that, The calcination temperature was 1100℃ and the time was 5 hours.

7. The preparation method according to claim 3, characterized in that, The pH value is 8.

8. A method for enhancing Sm by B-site modulation as described in claim 1 or 2 0.5 Sr 0.5 FeO 3-δ Application of oxygen reduction-active intermediate-temperature solid oxide fuel cell cathode materials in the preparation of intermediate-temperature solid oxide fuel cells.

9. The application according to claim 8, characterized in that, The electrolyte of the intermediate-temperature solid oxide fuel cell is Sm 0.2 Ce 0.8 O 2-δ The anode is NiO and Sm 0.2 Ce 0.8 O 2-δ Composite anode materials.

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