High-stability perovskite material applied to SOFC (Solid Oxide Fuel Cell) oxygen permeation membrane and preparation method of high-stability perovskite material

Abstract

The invention discloses a high-stability perovskite material applied to an SOFC oxygen permeation membrane and a preparation method thereof, and the preparation method comprises the following steps: weighing a strontium salt, a samarium salt, an iron salt, a niobium salt and a copper salt, adding into water, heating and stirring to obtain a metal ion solution; and adding a complexing agent into the metal ion solution, adjusting the pH value of the solution with ammonia water until the solution is in a gel state, drying, heating, and carrying out ball milling to obtain the high-stability perovskite material applied to the SOFC oxygen permeation membrane. Considering that cations such as Cu < 2 + > and Nb < 5 + > are doped in the B site of ABO3 type perovskite oxide to improve the performance of the ABO3 type perovskite oxide, the stability problem of long-time operation of the ABO3 type perovskite oxide is improved by fixing valence Nb < 5 + > to be doped in the B site of the SSCF perovskite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite ceramic materials, and in particular relates to a high-stability perovskite material used in SOFC oxygen permeable membranes and a preparation method thereof. Background Art

[0002] Sr at position A in SSCF 2+ For Sm 3+ The substitution of can significantly increase the oxygen vacancy concentration in the perovskite lattice, thereby increasing the oxygen ion conductivity. However, under this premise, enhancing its stability in CO2 environment is a research focus that needs to be focused on. b5+ 、Al 3+ 、Ga 3+ The stability of perovskite materials can be improved by increasing the acidity of the oxide. Metal oxides with higher acidity generally have higher stability in CO2 environments. In particular, Nb has been shown to be a very effective dopant in SrCo 0.9 M 0.1 O 3-δ (M = Cr, Fe, Al, Ga, Ti, Zr, Sn, V, Nb) doping, showed the best effect. For oxygen permeable membranes, generally, the improvement of stability is accompanied by a decrease in permeability, but only Nb 5+ The stability of doping is improved, and the oxygen permeability is also improved. 5+ Doping can not only improve the structural and compositional stability of perovskite materials, but also increase electronic conductivity. 5+ Introducing SrCo 0.2 Fe 0.8 O 3-δ In the process, the chemical adsorption of CO2 is inhibited and the SrCo 0.2 Fe 0.7 Nb 0.1 O 3-δ The catalytic activity and chemical stability of the catalyst are very good. At 750 °C, the Rp value is only 0.145 Ω·cm 2 , decreased by 21.2%. 3-δ Nb-doped 5+ Can significantly improve BaFeO 3-δ The perovskite based on the quartz crystal has the disadvantages of low oxygen vacancies, poor oxygen ion conductivity and permeability when the temperature is below 750 ℃. At 700 ℃, the Rp value is 0.102 Ω·cm 2 , the structural stability is greatly improved. 3-δ Introducing high-priced Nb 5+ It is beneficial to the stability of the cubic structure of the material. 2+ The introduction of SrCoO3-δ Oxygen vacancy concentration and reduce the Rp value. Nb 5+ and Cu 2+ The co-doping of MgO and FeO significantly increased the electrical conductivity to 550 S·cm at 400 ℃. -1 . Summary of the Invention

[0003] In view of this, the present invention aims to propose a high-stability perovskite material for use in SOFC oxygen permeable membranes and a preparation method thereof, so as to solve at least one technical problem in the background technology.

[0004] In order to solve the trade-off between stability and high performance in the design of the above perovskite materials, the present invention provides a promising design concept, considering that the B-site doping of ABO3 perovskite oxides with Cu 2+ and Nb 5+ The performance of the cations is improved by fixing the valence of Nb 5+ Doping the SSCF perovskite material at the B site improves its long-term stability. Calculations show that doping increases the configurational entropy from 1.19 R to 1.49 R. Although the material remains intermediate after adding the dopant, the increased configurational entropy contributes to improved stability.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows: A high-stability perovskite material used in SOFC oxygen permeable membrane, the high-stability perovskite material of SOFC oxygen permeable membrane is Sm 0.5 Sr 0.5 Cu 0.2 Fe 0.7 Nb 0.1 O 3-δ .

[0006] Furthermore, the material is SrFeO 3-δ Based on ABO3 type perovskite oxide, through low-valent Cu 2+ With fixed high valence Nb 5+ The B site is double doped.

[0007] A method for preparing a high-stability perovskite material for use in SOFC oxygen permeable membranes comprises the following steps: weighing strontium salt, samarium salt, iron salt, niobium salt, and copper salt, adding the salts to water, and heating and stirring to obtain a metal ion solution; adding a complexing agent to the metal ion solution, and adjusting the pH of the solution with aqueous ammonia until the solution becomes gel-like; and drying, heating, and ball milling to obtain the high-stability perovskite material for use in SOFC oxygen permeable membranes.

[0008] Further, the strontium salt includes strontium nitrate; Samarium salts include samarium nitrate hexahydrate; Iron salts include ferric nitrate nonahydrate; Niobium salts include ammonium niobium oxalate; Copper salts include copper nitrate.

[0009] Further, salt, samarium salt, iron salt, niobium salt and copper salt are added to water, and H2O2 and nitric acid are added while heating and stirring; Complexing agents include EDTA acid and citric acid; The molar ratio of total metal ions: EDTA acid: citric acid is 1:1:1.3-1.7.

[0010] Furthermore, the pH of the solution is adjusted to 6-8 with ammonia water, and the solution is continuously heated and stirred at 80-90°C until the solution becomes gel-like, and then placed in a drying oven at 140-160°C for 10-14 hours.

[0011] Furthermore, the drying and heating includes continuous heating and stirring to remove excess H2O2 until the solution becomes gel-like, and then placed in a drying oven for 24 hours. After it becomes black and fluffy, it is taken out and heated in a flat furnace to burn off organic matter. After stirring without sparks, it is placed in a muffle furnace for insulation.

[0012] Furthermore, the temperature of the muffle furnace is 900-1000°C.

[0013] Furthermore, the ball milling time of the high-stability perovskite material applied to the SOFC oxygen permeable membrane obtained after ball milling is at least 9 hours.

[0014] Furthermore, the high stability perovskite material prepared by the above-mentioned method for preparing a high stability perovskite material for SOFC oxygen permeable membrane is applied to SOFC oxygen permeable membrane. A high-stability perovskite material and its preparation method for SOFC oxygen permeable membrane. 2+ With fixed high valence Nb 5+ In the process of sol-gel synthesis of materials, in order to make the difficult-to-dissolve Nb 5+ The doping was successful, and H2O2 was used to oxidize the oxalate ions, and nitric acid was added to ensure the acidic conditions of the reaction, and finally Sm 0.5 Sr 0.5 Cu 0.2 Fe 0.7 Nb 0.1 O 3-δ(SSCFN) material. Nb doping significantly increases the material's configuration entropy (configuration entropy of 1.49 R). Although it is still a medium-entropy material, the increase in configuration entropy is beneficial to improving stability. 10 mol% Nb doping reduces the catalytic activity of the surface ORR reaction, thereby increasing its polarization impedance. Due to the obstruction of electron conduction by non-conductive Nb-O bonds, the electrical conductivity is also reduced compared to the undoped (SSCF). During the material preparation process, the dislocation density and oxygen vacancies are affected by the reasonable control of mechanical shear force and calcination temperature.

[0015] Compared with the prior art, the high-stability perovskite material and preparation method thereof for SOFC oxygen permeable membranes described in the present invention have the following advantages: The present invention uses ABO3 type perovskite oxide low-valent Cu 2+ With fixed high valence Nb 5+ The double doping of B site achieves a balance between oxygen vacancies and stability. At the same time, the preparation method of the material innovatively solves the problem of Nb 5+ The researchers overcame the doping challenge and ultimately successfully prepared a perovskite material that achieved a balance between performance and stability. They also conducted comparative analyses from the perspectives of phase structure, chemical state, and electrochemical performance. This enriched the design concepts of perovskite ceramic materials and has the potential for widespread application in materials such as SOFC electrodes and oxygen permeable membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings: Figure 1 (a is the XRD pattern of SSCF and SSCFN samples and b is the magnified view of the (110) crystal plane; Figure 2 As described in the present invention (a is the morphology of the SSCFN sample under TEM, b is high resolution; c is FFT); Figure 3 The grain morphology under EBSD of the present invention (a is SSCF; b is SSCFN); Figure 4 The grain orientation distribution of the perovskite material before and after Nb doping according to the present invention: (a and c are SSCF and SSCFN pole figures respectively; b and d are SSCF and SSCFN anti-pole figures respectively; Figure 5 Deconvoluted XPS spectra of the SSCF and SSCFN samples described in the present invention (a is Nb 3d; b is Fe 2p). DETAILED DESCRIPTION

[0017] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0018] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0019] A high-stability perovskite material used in SOFC oxygen permeable membrane, which is an ABO3 type perovskite oxide. 2+ With fixed high valence Nb 5+ The high-stability perovskite material achieves a balance between oxygen vacancies and stability and can be used in SOFC electrodes and oxygen-permeable membrane materials. The perovskite material typically contains less than 10 mol% Nb, less than 20 mol% Cu, and greater than 40% and less than 70% Sr.

[0020] A method for preparing a high-stability perovskite material for use in SOFC oxygen permeable membranes, the method comprising the following steps: (1) According to the chemical formula of the material, the required strontium salt, samarium salt, iron salt, niobium salt or copper salt is calculated and accurately weighed, and added to an appropriate amount of water, heated and stirred until completely dissolved to obtain a metal ion solution. Oxalate ions react with strontium ions to form strontium oxalate precipitate (SrC2O4), resulting in Nb 5+ It is difficult to dissolve, so H2O2 is used to oxidize the oxalate ions, and nitric acid is added to ensure acidic conditions for the reaction.

[0021] (2) Slowly add EDTA acid and citric acid, and adjust the pH of the solution with ammonia water. Continue heating and stirring to remove excess H2O2 until the solution becomes gel-like. Place it in a drying oven for 24 hours. After it becomes black and fluffy, take out the sample and heat it on a flat furnace to burn off the organic matter.

[0022] (3) After stirring without sparks, place it in a low-temperature muffle furnace to keep it warm, and the final required perovskite powder material is obtained.

[0023] (4) The obtained powder is ball-milled for a certain period of time.

[0024] In step (1), the strontium salt is Sr(NO3)2, the samarium salt is samarium nitrate hexahydrate (Sm(NO3)3·6H2O), the copper salt is copper nitrate (Cu(NO3)2), the niobium salt is ammonium niobium oxalate C4H4NNbO9.nH2O, and the iron salt is ferric nitrate nonahydrate (Fe(NO3)3·9H2O).

[0025] The pH value in step (1) is 6-8.

[0026] The heating and stirring temperature in step (2) is 80°C-90°C, the stirring speed is 150 rpm, and the stirring time is about 20 hours. During the preparation process, the total metal ion mass of the material: the mass of EDTA acid: the mass of citric acid = 1:1:1.5, the drying oven temperature is 150°C, and the time is about 12 hours.

[0027] The muffle furnace in step (3) is kept at a temperature of 950°C.

[0028] The ball milling time in step (4) is greater than 9 h.

[0029] A high-stability perovskite material for SOFC oxygen permeable membrane and a preparation method thereof, the specific steps are as follows: According to the chemical formula of the materials, the required strontium nitrate Sr(NO3)2, samarium nitrate hexahydrate (Sm(NO3)3·6H2O), copper nitrate (Cu(NO3)2), ammonium niobium oxalate C4H4NNbO9.nH2O and ferric nitrate nonahydrate (Fe(NO3)3·9H2O) were calculated and accurately weighed and heated and stirred until completely dissolved to obtain a metal ion solution. Oxalate ions react with strontium ions to form strontium oxalate precipitate (SrC2O4), resulting in Nb 5+ Since the oxalate ions are difficult to dissolve, H₂O₂ is used to oxidize them, and nitric acid is added to ensure acidic reaction conditions. EDTA and citric acid are slowly added in a ratio of 1:1:1.5, based on the total metal ion mass: EDTA acid mass: citric acid mass. Ammonia water is used to adjust the solution's pH to 6-8. The solution is heated and stirred continuously at 80°C-90°C until it forms a gel. The sample is then placed in a drying oven at 150°C for 12 hours. Once it becomes black and fluffy, it is removed and heated in a flat furnace to burn off organic matter. After stirring until sparks disappear, the sample is placed in a low-temperature muffle furnace and maintained at 950°C to obtain the desired perovskite powder. Finally, ball milling is performed for at least 9 hours to increase the dislocation density and oxygen vacancy concentration through mechanical shear.

[0030] like Figure 1 As shown in the figure, the XRD patterns of the SSCF and SSCFN samples prepared in this example and the (110) crystal plane magnification are shown. It is found that both samples have a main phase structure of cubic perovskite and contain a trace amount of orthorhombic crystal system. No niobium oxide phase (Nb2O 5） , which indicates that Nb is successfully incorporated into the perovskite structure. The diffraction peak intensity is relatively sharp and high, indicating that it has high crystallinity. Nb B-site doping can effectively stabilize the lattice structure of the disordered cubic perovskite with oxygen vacancies, and the ionic radius of the dopant has an impact on the structural stability of the doped compound and the maximum acceptable level of the parent compound. As mentioned earlier, dopants with similar ionic radii can produce lower association enthalpy values and more stable doping structures. Nb hexacoordinated with oxygen ions5+ The ionic radius (0.64 Å)

[267] is close to that of Fe3+ (0.65 Å). 5+ It has excellent matching properties as a dopant for SSCF. Figure 1 (b) is an enlarged view of the (110) crystal plane. After Nb doping, the XRD peak shifts to a lower angle, and the unit cell parameter increases from 3.907 Å to 3.915 Å. This is the result of the combined influence of the valence state of the B-site element and the oxygen vacancy concentration.

[0031] like Figure 2 As shown in Figure 1, the morphology of the SSCFN sample prepared in this example under TEM; (b) high resolution; (c) FFT diagram, the diffraction spots further prove the formation of the phase of the prepared material. Figure 2 (b) FFT analysis yields the diffraction pattern (c), which confirms the XRD analysis results based on calibration. The prepared SSCFN maintains the same perovskite structure as SSCF. Furthermore, Nb doping leads to a slight increase in the (100) interplanar spacing, corresponding to a shift in the XRD diffraction peak toward lower angles.

[0032] like Figure 3 Figure 2 shows the grain morphology of the materials prepared in this example under EBSD: (a) SSCF; (b) SSCFN. The SSCF grains are equiaxed and have a non-uniform size distribution. The SSCFN grains are non-equiaxed (elongated) and have a relatively uniform grain size distribution. This indicates that after Nb doping, the perovskite grains show a transition from a non-uniform to a uniform distribution.

[0033] like Figure 4 As shown in the figure, the grain orientation distribution of the perovskite material prepared in this embodiment: (a) and (c) are the SSCF and SSCFN pole figures respectively; (b) and (d) are the SSCF and SSCFN anti-pole figures respectively. Before doping with Nb, there are {001} parallel to the surface of the tablet. <001> Strong texture, while no texture exists on other crystal planes and directions. Figure 4 (b) and Figure 4 (d) shows the inverse pole figures (IPF) of SSCF and SSCFN grains respectively. It can be seen that after Nb doping, the {001} <001> The texture disappears, but a <101> / / Z, <114> / / X and <414> / / Y's high crystal orientation index texture. This indicates that Nb doping reduces the texture strength of the perovskite material to a certain extent, making the material more uniform and stable.

[0034] like Figure 5As shown in the figure, the deconvoluted XPS spectra of the SSCF and SSCFN samples prepared in this example are (a) Nb 3d; (b) Fe 2p. The signal peaks correspond to 3d 5 / 2 and 3d 3 / 2, showing double peaks, with binding energies of 206.89 eV and 209.68 eV, respectively. Studies have shown that the spin-orbit splitting energy of Nb 3d is 2.78 eV. 5 / 2 and 3D 3 / 2 The binding energy difference is 2.79 eV. Therefore, it is proved that the Nb element is successfully doped. 5+ Form exists. Figure 5 (b) shows the main peak Fe2p XPS spectra of SSCF and SSCFN, which are deconvoluted into two peaks at binding energies of 710.6 eV and 724.5 eV, corresponding to Fe 2p 3 / 2 and Fe 2p 1 / 2 , the satellite peaks are at 719.2 eV and 733.4 eV respectively. 3 / 2 The peak fitting was performed to quantify the existence form of Fe element in the studied perovskite material, and three peaks with binding energies of 712.3 eV, 710.5 eV and 709.4 eV were obtained, corresponding to Fe 4+ 2p 3 / 2 、Fe3+ 2p 3 / 2 and F e2+ 2p 3 / 2 .

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-stability perovskite material for SOFC oxygen permeable membrane, characterized by: The high stability perovskite material of SOFC oxygen permeable membrane is Sm 0.5 Sr 0.5 Cu 0.2 Fe 0.7 Nb 0.1 O 3-δ .

2. The high-stability perovskite material for SOFC oxygen permeable membrane according to claim 1, characterized in that: Materials in SrFeO 3-δ Based on ABO3 type perovskite oxide, through low-valent Cu 2+ With fixed high valence Nb 5+ B-site dual doping; The doped Nb content is less than 10 mol%, the Cu content is less than 20 mol%, and the Sr content is higher than 40% and lower than 70%.

3. The method for preparing a high-stability perovskite material for use in a SOFC oxygen permeable membrane according to claim 1 or 2, characterized in that: The method comprises the following steps: weighing strontium salt, samarium salt, iron salt, niobium salt and copper salt, adding the salts to water, heating and stirring to obtain a metal ion solution; adding a complexing agent to the metal ion solution, adjusting the pH value of the solution with ammonia water until the solution becomes gel-like, drying, heating and ball milling to obtain a high-stability perovskite material used for SOFC oxygen permeable membrane.

4. The method for preparing a high-stability perovskite material for use in a SOFC oxygen permeable membrane according to claim 3, wherein: Strontium salts include strontium nitrate; Samarium salts include samarium nitrate hexahydrate; Iron salts include ferric nitrate nonahydrate; Niobium salts include ammonium niobium oxalate; Copper salts include copper nitrate.

5. The method for preparing a high-stability perovskite material for use in a SOFC oxygen permeable membrane according to claim 3, wherein: Salt, samarium salt, iron salt, niobium salt and copper salt are added to water, and H2O2 and nitric acid are added while heating and stirring; Complexing agents include EDTA acid and citric acid; The molar ratio of total metal ions: EDTA acid: citric acid is 1:1:1.3-1.

7.

6. The method for preparing a high-stability perovskite material for use in a SOFC oxygen permeable membrane according to claim 3, wherein: Adjust the pH of the solution to 6-8 with ammonia water, continue heating and stirring at 80-90°C until the solution becomes gel-like, and then place it in a drying oven at 140-160°C for 10-14 hours.

7. The method for preparing a high-stability perovskite material for use in a SOFC oxygen permeable membrane according to claim 3, wherein: Drying and heating involves continuous heating and stirring to remove excess H2O2 until the solution becomes gel-like, then placed in a drying oven for 24 hours. After it becomes black and fluffy, it is taken out and heated in a flat furnace to burn off organic matter. After stirring without sparks, it is placed in a muffle furnace for insulation.

8. The method for preparing a high-stability perovskite material for use in a SOFC oxygen permeable membrane according to claim 3, wherein: The temperature of the muffle furnace is 900-1000℃.

9. The method for preparing a high-stability perovskite material for use in a SOFC oxygen permeable membrane according to claim 3, wherein: The ball milling time of the high-stability perovskite material used for SOFC oxygen permeable membrane obtained after ball milling is at least 9 hours.

10. The method for preparing a high-stability perovskite material for use in SOFC oxygen permeable membranes according to any one of claims 3 to 9, wherein the high-stability perovskite material prepared is used in SOFC oxygen permeable membranes.

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