Method for selectively removing enriched and segregated elements on surface of perovskite-based air electrode, and use thereof

Abstract

Provided are a method for selectively removing enriched and segregated elements on the surface of a perovskite-based air electrode, and the use thereof. The method comprises: treating a perovskite-based air electrode or electrode powder in an alkali liquor, and then washing and drying same, wherein the concentration of the alkali liquor is 0.01-10 mol L-1; the pH value of the alkali liquor is greater than 7; and the treatment time is 1-600 min. The method greatly increases the active sites on the surface of the electrode, significantly improves the intrinsic activity, and also improves the stability and water resistance of the electrode. The method can effectively improve the peak power density of a solid oxide fuel cell and the current density of a solid oxide electrolytic cell, and can also improve the long-term stability of the cell and the electrolytic cell. The air electrode obtained by means of the method is used in the solid oxide fuel cell and the solid oxide electrolytic cell.

Description

Method and application for selectively removing elements enriched and segregated on the surface of perovskite-based air electrodes Technical Field

[0001] The present invention relates to the technical field of solid oxide fuel cells and electrolytic cells (SOFC / SOEC, collectively referred to as SOC), and in particular to a method and application for selectively removing elements enriched and segregated on the surface of a perovskite-based air electrode. Background Art

[0002] Solid oxide cell (SOC)-based energy conversion systems have the potential to become the cleanest and most efficient systems for reversible conversion between electricity and chemical fuels due to their high efficiency, low emissions, and excellent fuel flexibility. However, the widespread implementation of this technology has been hindered by the lack of high-performance electrode materials. Perovskite-based materials (with the general structural formula ABO 3-δ 、A n+1 B n O 3n+1 AA'B2O 5+δ ) is composed of rare earth metals or alkaline earth metals at the A position and transition metals at the B position. Due to its multiple electron and ion conductivity, it shows great potential for application as a SOC air electrode. However, during material preparation or battery operation, the enrichment and segregation of A-site cations are prone to occur on the surface or near the interface of perovskite-based materials. The enriched or segregated cation oxides have poor electron and ion transport performance and electrocatalytic activity, and easily react with water and carbon dioxide in the air to form inert hydroxides and carbonates, thereby covering the active sites on the electrode surface. This not only severely slows down the reaction kinetics of the electrode, but also greatly reduces its durability and service life.

[0003] In addition, the transition metal elements in perovskite are generally considered to be the active centers of electrode reactions. In order to improve the electrode activity, the B-site active center should be exposed on the electrode surface as much as possible.

[0004] Summary of the Invention

[0005] In light of this, the present invention provides an alkaline solution treatment method for selectively removing elements concentrated and segregated on the surface of perovskite-based air electrodes. The treated air electrodes exhibit excellent catalytic performance and long-term stability in solid oxide fuel cells and solid oxide electrolyzers. This method does not damage the overall cell structure or require complex or expensive auxiliary equipment, making it simple to operate and amenable to large-scale implementation.

[0006] Another object of the present invention is to provide the use of the air electrode or electrode powder obtained by the above method in solid oxide fuel cells and solid oxide electrolysis cells.

[0007] The technical solution of the present invention is:

[0008] A method for selectively removing elements enriched and segregated on the surface of a perovskite-based air electrode comprises the following steps: treating the perovskite-based air electrode or electrode powder in an alkaline solution, followed by washing and drying;

[0009] The concentration of the alkali solution is 0.01 to 10 mol L -1 ; The pH value of the alkali solution is greater than 7;

[0010] The treatment time is 1 to 600 minutes.

[0011] Preferably, the concentration of the alkali solution is 0.2 to 2 mol L -1 ; The processing time is 20 to 120 minutes.

[0012] The alkali solution is one or more of a strong alkali solution, a weak alkali solution or a solution of a strong base and a weak acid salt, including but not limited to solutions of lithium hydroxide, potassium hydroxide, sodium hydroxide, calcium hydroxide, barium hydroxide, cesium hydroxide, ammonia water, sodium carbonate, sodium bicarbonate, etc.; preferably a strong alkali solution.

[0013] The alkali solution is one or more of potassium hydroxide, sodium hydroxide and lithium hydroxide solutions.

[0014] The temperature of the alkali solution is room temperature to 100° C.; the alkali solution is a flowing alkali solution or a static alkali solution; the flowing alkali solution is based on the alkali solution, and auxiliary means including but not limited to stirring, flushing, ultrasound, etc. are used to achieve dynamic disturbance of the alkali solution.

[0015] The perovskite-based air electrode is an air electrode composed of perovskite-type oxides, perovskite-like oxides, double perovskite oxides, and a composite air electrode containing one or more of perovskite-type oxides, perovskite-like oxides, and double perovskite oxides;

[0016] The electrode powder is an air electrode powder or raw material composed of perovskite oxide, perovskite-like oxide, double perovskite oxide, or a composite air electrode powder or raw material containing one or more of perovskite oxide, perovskite-like oxide, and double perovskite oxide;

[0017] The molecular formula of the perovskite oxide is ABO 3-δ ; wherein the cation at position A is one or more rare earth metal ions or alkaline earth metal ions, preferably Ba, Sr or La; the cation at position B is one or more transition metal ions, preferably Fe, Co, Ni, Mn, Cu or Zn; 0≤δ≤1.

[0018] The molecular formula of the perovskite-like oxide is A n+1 B nO 3n+1 ; Wherein the A-position cation is one or more rare earth metal ions or alkaline earth metal ions, preferably La, Pr, Gd; the B-position cation is one or more transition metal ions, preferably Fe, Co, Ni, Mn, Cu or Zn; n≥1.

[0019] The molecular formula of the double perovskite oxide is AA'B2O 5+δ ; Wherein the cations at positions A and A' are one or more rare earth metal ions or alkaline earth metal ions, and A and A' cannot be the same, A is preferably La, Pr, Sm, Gd, A' is preferably Ba, Sr, Ca, and the cation at position B is one or more transition metal ions, preferably Fe, Co, Ni, Mn, Cu or Zn; 0≤δ≤1.

[0020] The cleaning liquid is water or a volatile organic solvent;

[0021] The organic solvent includes but is not limited to methanol, ethanol, isopropanol, acetone, etc. The number of times of washing is 3 to 10 times, and the pH value after the last washing is controlled to be no greater than 7;

[0022] The mass volume ratio of perovskite air electrode or electrode powder to alkali solution is 0.01~100g L -1 .

[0023] The drying temperature is 60-300° C., and the drying time is greater than 2 hours.

[0024] After being treated by the above method, the electrode powder can be used to prepare the air electrode of the fuel cell, and has better performance than the electrode prepared from the untreated electrode powder.

[0025] The surface enriched and segregated elements to be removed are one or more of the enriched layer of alkaline earth metal elements or rare earth metal elements on the surface of the perovskite lattice, oxides of alkaline earth metal elements or rare earth metal elements, and products produced by the reaction of alkaline earth metal elements or rare earth metal elements with water or carbon dioxide in the environment.

[0026] The method proposed in the present invention has the following advantages in treating electrodes and electrode powders with alkaline solutions: both alkaline solutions and acidic solutions can remove elements enriched or segregated on the surface, but compared with acidic liquids, perovskite materials are more stable in alkaline liquids. While removing elements enriched or segregated on the electrode surface, it is not easy to damage the structure of the electrode material, and has high selectivity in removing elements enriched or segregated on the surface.

[0027] In the present invention, the treated electrode and electrode powder are tested by X-ray diffraction (XRD) and the phase structure does not change and the peak position does not shift, indicating that the removed alkaline earth metal elements and rare earth metal elements are enriched and segregated elements on the electrode surface. If the XRD characterization shows that the phase structure has changed, it means that the electrode structure has been damaged.

[0028] The air electrode is an electrode in a solid oxide fuel cell and / or a solid oxide electrolysis cell.

[0029] The air electrode obtained by the method is used in solid oxide fuel cells and solid oxide electrolysis cells.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] After alkaline solution treatment, the alkaline earth metal elements enriched and segregated on the surface of the perovskite-based air electrode are selectively removed, which greatly increases the active sites on the electrode surface and significantly improves the intrinsic activity. At the same time, the stability and water resistance of the electrode are improved. Alkaline solution treatment can effectively increase the peak power density of the solid oxide fuel cell and the current density of the solid oxide electrolyzer, and improve the long-term stability of the battery and electrolyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a diagram of PrBa in Example 1 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF) Morphology comparison before and after KOH solution treatment, (a) PBSCF before treatment, (b) PBSCF after treatment;

[0033] FIG2 is a graph showing the percentage concentrations of Pr, Ba, Sr, Co, and Fe in the KOH solution of the PBSCF treated in Example 1, as determined by ICP-OES.

[0034] FIG3 is a comparison of the phase structures of PBSCF before and after treatment with KOH solution in Example 1, (a) is PBSCF before treatment, and (b) is PBSCF after treatment;

[0035] Figure 4 is a diagram of PrBa in Example 2 0.8 Ca 0.2 Co2O 5+δ (PBCC) Morphology comparison before and after KOH solution treatment, (a) PBCC before treatment, (b) PBCC after treatment;

[0036] FIG5 is a comparison of the phase structures of PBCC before and after KOH solution treatment in Example 2, (a) is PBCC before treatment, and (b) is PBCC after treatment;

[0037] FIG6 is a symmetrical PBSCF battery (with BaZr) in Example 3 without KOH solution treatment. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3 as electrolyte) and PBSCF symmetric battery treated with KOH solution (with BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 Comparison of polarization impedance at different temperatures (with O3 as electrolyte);

[0038] FIG. 7 is a symmetrical PBCC battery (with BaZr) not treated with KOH solution in Example 4. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3 as electrolyte) and PBCC symmetric battery treated with KOH solution (with BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 Comparison of polarization impedance at different temperatures (with O3 as electrolyte);

[0039] FIG8 is a La sample in Example 5 that has not been treated with KOH solution. 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δ (LSCF) symmetric battery (based on BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3 as electrolyte) and LSCF treated with KOH solution (with BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 Comparison of polarization impedance of symmetrical battery with O3 as electrolyte at different temperatures;

[0040] FIG. 9 is a symmetrical LSCF cell (with Sm 0.2 Ce 0.8 O 1.9 as electrolyte) and LSCF symmetric cells treated with KOH solution (with Sm 0.2 Ce 0.8 O 1.9 Comparison of polarization impedance at different temperatures (electrolyte);

[0041] FIG10 is a comparison of the discharge mode IVP curves of the PBSCF single cell without KOH solution treatment and the PBSCF single cell treated with KOH solution at 650° C. in Example 7;

[0042] FIG11 is a comparison of IV curves of the electrolysis mode of the PBSCF single cell without KOH solution treatment and the PBSCF single cell treated with KOH solution at 650° C. in Example 7;

[0043] Figure 12 shows the discharge current density of the PBSCF single cell treated with KOH solution at 650°C in Example 7 at 1A cm -2 Durability test under ;

[0044] Figure 13 shows the electrolysis current density of the PBSCF single cell treated with KOH solution at 600°C in Example 7 at a current density of 0.5 A cm -2 Durability test under ;

[0045] Figure 14 shows the PBSCF single cell treated with KOH solution in Example 7 at 650°C with a constant current density of ±0.5 A cm -2 Conduct reversible cycle stability tests of fuel cells and electrolytic cells under

[0046] Figure 15 is a graph showing the reaction of Example 8, Example 6, and Comparative Example 1 with 2 mol L -1 LSCF symmetric cells (with Sm 0.2 Ce 0.8 O 1.9 Comparison of polarization impedance at different temperatures (electrolyte);

[0047] Figure 16 is a comparative example 2, Example 9, Example 6 with different concentrations (0 mol L -1 , 0.2 mol L -1 , 2 mol L -1 ) LSCF symmetric cell treated with KOH solution for 2h (with Sm 0.2 Ce 0.8 O 1.9 Comparison of polarization impedance at different temperatures. DETAILED DESCRIPTION

[0048] The present invention will be described in further detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0049] Example 1

[0050] Weigh the PrBa synthesized by sol-gel method0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ The double perovskite oxide (PBSCF) was calcined at 950 °C for 2 h, which was the same as the calcination step for preparing the air electrode. Then 1 g of the calcined sample was weighed and immersed in 15 mL of 2 mol L -1 The mixture was stirred at 300 rpm for 2 h in KOH solution, washed with deionized water and filtered three times, and then dried in an oven at 120°C for 5 h.

[0051] Figure 1 is a diagram of PrBa in Example 1 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF) Morphology comparison before and after KOH solution treatment, (a) PBSCF before treatment, (b) PBSCF after treatment;

[0052] FIG2 is a graph showing the percentage concentrations of Pr, Ba, Sr, Co, and Fe in the KOH solution of the PBSCF treated in Example 1, as determined by ICP-OES.

[0053] FIG3 is a comparison of the phase structures of PBSCF before and after treatment with KOH solution in Example 1, wherein (a) is PBSCF before treatment and (b) is PBSCF after treatment.

[0054] It can be seen from Figure 1 that the segregated species on the surface of PBSCF treated with KOH solution are removed.

[0055] As can be seen from Figure 2, the elements dissolved from PBSCF in KOH solution are mainly Ba and Sr, which account for 83.7% and 16% of the dissolved elements (percentage of substance), respectively.

[0056] As can be seen from Figure 3, the phase structure of PBSCF treated with KOH solution and without KOH solution did not change significantly.

[0057] Example 2

[0058] Weigh the PrBa synthesized by sol-gel method 0.8 Ca 0.2 Co2O 5+δ The double perovskite oxide (PBCC) was calcined at 950 °C for 2 h, which was the same as the calcination step for preparing the air electrode. The calcined sample was then immersed in 15 mL of 2 mol L -1The mixture was stirred at 300 rpm for 2 h in KOH solution, washed with deionized water and filtered three times, and then dried in an oven at 120°C for 5 h.

[0059] Figure 4 is a diagram of PrBa in Example 2 0.8 Ca 0.2 Co2O 5+δ (PBCC) Morphology comparison before and after KOH solution treatment, (a) PBCC before treatment, (b) PBCC after treatment;

[0060] FIG5 is a comparison of the phase structures of PBCC before and after KOH solution treatment in Example 2, (a) is PBCC before treatment, and (b) is PBCC after treatment.

[0061] It can be seen from Figure 4 that the segregated species on the surface of PBCC treated with KOH solution are removed.

[0062] As can be seen from Figure 5, the phase structure of PBCC treated with KOH solution and without KOH solution did not change significantly.

[0063] Example 3

[0064] The prepared BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3 as electrolyte, PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ A symmetrical cell with double perovskite oxide (PBSCF) as the air electrode was immersed in 15 mL of 2 mol L -1 The air electrode was placed in a KOH solution and stirred at 300 rpm for 2 h. The air electrode was then rinsed 10 times with deionized water. The pH value of the wastewater after the last rinse did not exceed 7. The symmetrical cell was then placed in a 120 °C oven and dried for 5 h.

[0065] FIG6 is a symmetrical PBSCF battery (with BaZr) in Example 3 without KOH solution treatment. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3 as electrolyte) and PBSCF symmetric battery treated with KOH solution (with BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 Comparison of polarization impedance at different temperatures (with O3 as electrolyte).

[0066] As can be seen from Figure 6, compared with the symmetrical battery with untreated air electrode, after being treated with KOH solution, PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ The polarization impedance of the air electrode at each temperature decreases significantly.

[0067] Example 4

[0068] The prepared BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3 as electrolyte, PrBa 0.8 Ca 0.2 Co2O 5+δ A symmetrical cell with double perovskite oxide (PBCC) as the air electrode was immersed in 15 mL of 2 mol L -1 The air electrode was placed in a KOH solution and stirred at 300 rpm for 2 h. The air electrode was then rinsed 10 times with deionized water. The pH value of the wastewater after the last rinse did not exceed 7. The symmetrical cell was then placed in a 120 °C oven and dried for 5 h.

[0069] FIG. 7 is a symmetrical PBCC battery (with BaZr) not treated with KOH solution in Example 4. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3 as electrolyte) and PBCC symmetric battery treated with KOH solution (with BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 Comparison of polarization impedance at different temperatures (with O3 as electrolyte).

[0070] As can be seen from Figure 7, compared with the symmetrical battery with untreated air electrode, after being treated with KOH solution, PrBa 0.8 Ca 0.2 Co2O 5+δ The polarization impedance of the air electrode at each temperature decreases significantly.

[0071] Example 5

[0072] The prepared BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3 is the electrolyte, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δA symmetrical cell with (LSCF) perovskite oxide as the air electrode was immersed in 15 mL of 2 mol L -1 The air electrode was placed in a KOH solution and stirred at 300 rpm for 2 h. The air electrode was then rinsed 10 times with deionized water. The pH value of the wastewater after the last rinse did not exceed 7. The symmetrical cell was then placed in a 120 °C oven and dried for 5 h.

[0073] FIG8 is a La sample in Example 5 that has not been treated with KOH solution. 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δ (LSCF) symmetric battery (based on BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3 as electrolyte) and LSCF treated with KOH solution (with BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 Comparison of polarization impedance of symmetric batteries (with O3 as electrolyte) at different temperatures.

[0074] As can be seen from Figure 8, compared with the symmetrical battery with untreated air electrode, after being treated with KOH solution, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δ The polarization impedance of the air electrode at each temperature decreases significantly.

[0075] Example 6

[0076] The prepared Sm 0.2 Ce 0.8 O 1.9 As electrolyte, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δ A symmetrical cell with (LSCF) perovskite oxide as the air electrode was immersed in 15 mL of 2 mol L -1 The air electrode was placed in a KOH solution and stirred at 300 rpm for 2 h. The air electrode was then rinsed 10 times with deionized water. The pH value of the wastewater after the last rinse did not exceed 7. The symmetrical cell was then placed in a 120 °C oven and dried for 5 h.

[0077] FIG. 9 is a symmetrical LSCF cell (with Sm 0.2 Ce 0.8 O 1.9as electrolyte) and LSCF symmetric cells treated with KOH solution (with Sm 0.2 Ce 0.8 O 1.9 Comparison of polarization impedance at different temperatures.

[0078] As can be seen from Figure 9, compared with the symmetrical battery with untreated air electrode, after being treated with KOH solution, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δ The polarization impedance of the air electrode at each temperature decreases significantly.

[0079] Example 7

[0080] The prepared BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O3-NiO (mass ratio is 2:3) is the anode, BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 The proton ceramic battery with O3 as electrolyte and PBSCF double perovskite oxide as air electrode was used. The area outside the air electrode was taped to prevent the alkaline solution from entering the porous anode, and then immersed in 15 mL of 2 mol L -1 The mixture was stirred at 300 rpm in a KOH solution for 2 h, and then the air electrode of the single cell was rinsed 10 times with deionized water. The pH value of the rinse wastewater did not exceed 7. The single cell was then placed in a 120 °C oven and dried for 5 h.

[0081] FIG10 is a comparison of the discharge mode IVP curves of the PBSCF single cell without KOH solution treatment and the PBSCF single cell treated with KOH solution at 650°C in Example 7; FIG11 is a comparison of the electrolysis mode IV curves of the PBSCF single cell without KOH solution treatment and the PBSCF single cell treated with KOH solution at 650°C in Example 7; FIG12 is a comparison of the discharge mode IV curves of the PBSCF single cell treated with KOH solution at 650°C in Example 7 -2 Durability test under; Figure 13 is a PBSCF single cell treated with KOH solution in Example 7 at 600 ° C, the electrolysis current density is 0.5A cm -2 Durability test under; Figure 14 is a PBSCF single cell treated with KOH solution in Example 7 at 650 ° C, with a constant current density of ± 0.5A cm -2 The reversible cycle stability test of fuel cells and electrolytic cells was carried out under the following conditions.

[0082] As can be seen from Figure 10, compared with the single cell with untreated air electrode, the single cell treated with KOH solution has a higher peak power density at 650°C.

[0083] As can be seen from Figure 11, compared with the single cell with untreated air electrode, the single cell treated with KOH solution has a higher electrolysis current density at 650°C.

[0084] As can be seen from Figure 12, after KOH solution treatment, the PBSCF single cell exhibits excellent durability in the constant current discharge test at 650°C.

[0085] As can be seen from Figure 13, after being treated with KOH solution, the PBSCF single cell exhibits excellent durability in the constant current electrolysis test at 600°C.

[0086] As can be seen from Figure 14, after being treated with KOH solution, the PBSCF single cell exhibited excellent cycle stability in constant current discharge and electrolysis reversible cycle tests.

[0087] Example 8

[0088] The prepared Sm 0.2 Ce 0.8 O 1.9 As electrolyte, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δ A symmetrical cell with (LSCF) perovskite oxide as the air electrode was immersed in 15 mL of 2 mol L -1 The air electrode was placed in a KOH solution and stirred at 300 rpm for 20 min. The air electrode was then rinsed 10 times with deionized water. The pH value of the waste liquid after the last rinse did not exceed 7. The symmetrical cell was then placed in a 120 °C oven and dried for 5 h.

[0089] Example 9

[0090] The prepared Sm 0.2 Ce 0.8 O 1.9 As electrolyte, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δ A symmetrical cell with (LSCF) perovskite oxide as the air electrode was immersed in 15 mL of 0.2 mol L -1 The battery was placed in a KOH solution and stirred at 300 rpm for 2 h. The air electrode was then rinsed 10 times with deionized water. The symmetrical battery was then placed in an oven at 120 °C and dried for 5 h.

[0091] Comparative Example 1

[0092] The prepared Sm 0.2 Ce 0.8 O 1.9 As electrolyte, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δ A symmetrical cell with (LSCF) perovskite oxide as the air electrode was immersed in 15 mL of 2 mol L -1 The air electrode was placed in a KOH solution and stirred at 300 rpm for 300 min. The air electrode was then rinsed 10 times with deionized water. The pH value of the waste liquid from the last rinse did not exceed 7. The symmetrical cell was then placed in a 120 °C oven and dried for 5 h.

[0093] Comparative Example 2

[0094] The prepared Sm 0.2 Ce 0.8 O 1.9 As electrolyte, La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 5+δ The symmetrical cell with (LSCF) perovskite oxide as the air electrode was immersed in 15 mL of deionized water and stirred at 300 rpm for 2 h. The air electrode was then rinsed 10 times with deionized water, and the symmetrical cell was then placed in a 120 °C oven to dry for 5 h.

[0095] Figure 15 is a graph showing the reaction of Example 8, Example 6, and Comparative Example 1 with 2 mol L -1 LSCF symmetric cells (with Sm 0.2 Ce 0.8 O 1.9 Comparison of polarization impedance at different temperatures.

[0096] As can be seen from Figure 15, the LSCF electrode -1 The treatment time in KOH solution has different effects on the electrode activity test. When the treatment time is 20-120 min, the electrode activity is significantly improved. When the treatment time reaches 300 min, the electrode activity decreases compared with 20-120 min.

[0097] Figure 16 is a comparative example 2, Example 9, Example 6 with different concentrations (0 mol L -1 , 0.2 mol L -1 , 2 mol L-1 ) LSCF symmetric cell treated with KOH solution for 2h (with Sm 0.2 Ce 0.8 O 1.9 Comparison of polarization impedance at different temperatures.

[0098] As can be seen from Figure 16, the LSCF electrode -1 KOH solution and 2 mol L -1 The LSCF electrode has a good treatment effect in KOH solution, but the electrode activity becomes worse after treatment in deionized water, which shows that the LSCF electrode needs to have a good treatment effect in a certain concentration of KOH solution.

Claims

1. A method for selectively removing the enriched and segregated elements on the surface of a perovskite-based air electrode, characterized in that: It includes the following steps: Treat the perovskite-based air electrode or electrode powder in an alkaline solution, then wash and dry it; The concentration of the lye is 0.01 to 10 mol / L -1 ; the pH value of the lye is greater than 7; The treatment time is 1 to 600 min.

2. The method for selectively removing surface-enriched and segregated elements of a perovskite-based air electrode according to claim 1, wherein: The concentration of the lye is 0.2 to 2 mol / L -1 ; The treatment time is 20 to 120 min.

3. The method for selectively removing surface-enriched and segregated elements of a perovskite-based air electrode according to claim 1, wherein: The alkaline solution is one or more of a strong alkaline solution, a weak alkaline solution, or a solution of a strong-weak-acid salt.

4. The method for selectively removing the enriched and segregated elements on the surface of the perovskite-based air electrode according to claim 3, wherein: The alkaline solution is a strong alkaline solution.

5. The method for selectively removing the enriched and segregated elements on the surface of the perovskite-based air electrode according to claim 4, wherein: The alkaline solution is one of potassium hydroxide, sodium hydroxide, or lithium hydroxide solution.

6. The method for selectively removing the enriched and segregated elements on the surface of the perovskite-based air electrode according to claim 1, characterized in that: The perovskite-based air electrode is an air electrode composed of perovskite-type oxides, perovskite-like oxides, double perovskite oxides, and a composite air electrode containing one or more of perovskite-type oxides, perovskite-like oxides, and double perovskite oxides; The electrode powder is an air electrode powder or raw material composed of perovskite-type oxides, perovskite-like oxides, double perovskite oxides, and a composite air electrode powder or raw material containing one or more of perovskite-type oxides, perovskite-like oxides, and double perovskite oxides; The cleaning solution for the cleaning is water or a volatile organic solvent; The surface-enriched and segregated elements are one or more of an enrichment layer of alkaline earth metal elements or rare earth metal elements on the perovskite lattice surface, oxides of alkaline earth metal elements or rare earth metal elements, and products generated by the reaction of alkaline earth metal elements or rare earth metal elements with water or carbon dioxide in the environment.

7. The method for selectively removing surface-enriched and segregated elements of a perovskite-based air electrode according to claim 6, wherein: The molecular formula of the perovskite oxide is ABO 3-δ ; wherein the A-site cation is one or more of rare earth metal ions or alkaline earth metal ions; the B-site cation is one or more of transition metal ions; 0 ≤ δ ≤ 1; The molecular formula of the perovskite-like oxide is A n+1 B n O 3n+1 ; where the A-site cation is one or more of rare earth metal ions or alkaline earth metal ions; the B-site cation is one or more of transition metal ions; n≥1; The molecular formula of the double perovskite oxide is AA’B2O 5+δ ; where the cations at the A and A’ sites are one or more of rare earth metal ions or alkaline earth metal ions, and A and A’ cannot be the same; the cations at the B site are one or more of transition metal ions; 0 ≤ δ ≤ 1; The organic solvent is one or more of methanol, ethanol, isopropanol, and acetone.

8. The method for selectively removing the enriched and segregated elements on the surface of the perovskite-based air electrode according to claim 7, characterized in that: The molecular formula of the perovskite oxide is ABO 3-δ ; wherein the A-site cation is Ba, Sr or La; the B-site cation is Fe, Co, Ni, Mn, Cu or Zn; The molecular formula of the perovskite-like oxide is A n+1 B n O 3n+1 ; wherein the A-site cation is La, Pr, or Gd; the B-site cation is Fe, Co, Ni, Mn, Cu, or Zn; The molecular formula of the double perovskite oxide is AA'B2O 5+δ ; A is La, Pr, Sm, Gd, A' is Ba, Sr, Ca, and the B-site cation is Fe, Co, Ni, Mn, Cu or Zn.

9. The method for selectively removing surface-enriched and segregated elements of a perovskite-based air electrode according to claim 1, wherein: The number of cleaning times is 3 to 10 times, controlling the pH value of the cleaning agent after the last washing to be not greater than 7; the drying temperature is 60 to 300 °C, and the drying time is greater than 2 h.

10. Application of the air electrode obtained by the method according to any one of claims 1 to 9 in a solid oxide fuel cell and a solid oxide electrolyzer.

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