Highly catalytically active air electrode, method for its production and solid oxide fuel cell

Abstract

The application discloses a high-catalytic-activity air electrode and a preparation method and a solid oxide fuel cell thereof, and relates to the technical field of batteries. 0.5 Al 0.25 Cu 0.25 O 3‑δ material, 0≤δ<1; the CaFe 0.5 Al 0.25 Cu 0.25 O 3‑δ material is loaded on the electrolyte after acid treatment and sintered at 800-1100 DEG C; a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 is used for impregnation, and the sintering at 800-1100 DEG C is continued, and the air electrode is obtained.The application further provides a solid oxide fuel cell comprising the air electrode.The application has the beneficial effects that the CaFe 0.5 Al 0.25 Cu 0.25 O 3‑δ material is prepared by using low-cost non-precious metal and non-rare earth element raw materials, and the production cost is reduced; the CaFe 0.5 Al 0.25 Cu 0.25 O 3‑δ material is treated and optimized, the catalytic activity is improved, and the polarization impedance is reduced.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a highly catalytically active air electrode and its preparation method, and a solid oxide fuel cell. Background Technology

[0002] A solid oxide fuel cell (SOFC) is an all-solid-state chemical power generation device that efficiently and environmentally converts the chemical energy stored in fuel and oxidant into electrical energy directly at medium to high temperatures. The simplest SOFC consists of an air electrode (cathode), an electrolyte, and an anode. The air electrode is mainly responsible for the oxygen reduction reaction, promoting the reduction of oxygen into oxygen ions, and facilitating efficient charge transfer at the electrolyte interface.

[0003] Currently, there are many high-performance air electrode materials, but almost all of them rely heavily on rare earth elements, such as BaCo. 0.4 Fe 0.4 Zr 0.1 Y 0.1 O3,Sr 0.9 Cs 0.1 Co 0.9 Nb 0.1 O3, PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 High-performance air electrode materials such as O5 are needed. High material costs are a major factor limiting the development and industrialization of SOFCs. There is a need for an air electrode synthesized using only common non-precious metal elements (Ca, Fe, Al, Cu, etc.) that do not rely on rare earth elements to reduce the material cost of SOFCs. However, air electrodes synthesized solely from non-precious metals often have limited catalytic activity, resulting in poor overall electrochemical performance of SOFCs. Therefore, a series of optimization studies are required to improve their catalytic activity. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a highly catalytically active air electrode and its preparation method, as well as a solid oxide fuel cell. One aspect of this invention is the use of low-cost non-precious metal and non-rare earth element raw materials to prepare CaFe... 0.5 Al 0.25 Cu 0.25 O 3-δ Materials, thereby reducing production costs; on the other hand, through the analysis of CaFe 0.5 Al 0.25 Cu 0.25 O 3-δThe air electrode was optimized to improve its catalytic activity and reduce its polarization resistance.

[0005] This invention synthesizes a low-cost composite perovskite air electrode CaFe using the sol-gel method. 0.5 Al 0.25 Cu 0.25 O 3-δ (0 < δ < 1), this cathode does not contain noble metals or rare earth metals, but only uses common non-noble metals. This is similar to the widely used SOFC air electrode material BaCo reported in Science (2015). 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ In comparison, the air electrode CaFe of the present invention 0.5 Al 0.25 Cu 0.25 O 3-δ The cost of CFAC (carbon dioxide-electrolyte complex) material was reduced by nearly 75%. Furthermore, the catalytic activity and polarization resistance of CFAC prepared solely by the sol-gel method are not competitive in the market compared to classic materials containing noble metals and rare earth elements. This invention improves and optimizes CFAC by exploring and optimizing electrode sintering temperature, acid treatment of the electrode-electrolyte interface, and electrode impregnation, successfully reducing the polarization resistance of CFAC and improving the power output of full cells based on this air electrode. The final optimized air electrode has a polarization resistance of 0.026 Ω / cm. 2 (750℃), the power density in a proton conductor fuel cell (PCFC) at 750℃ is 632 mW / cm³. 2 In an oxygen ion conductor fuel cell (SOFC), the power density at 850°C is 577 mW / cm³. 2 Considering both cost and performance, it possesses significant market competitiveness.

[0006] The technical solution of the present invention is as follows:

[0007] A first aspect of the present invention provides a method for preparing a highly catalytically active air electrode, comprising the following steps:

[0008] S1, Synthesis of CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ Materials, where 0 ≤ δ < 1;

[0009] S2, the CaFe 0.5 Al 0.25 Cu 0.25 O 3-δThe material is loaded onto an acid-treated electrolyte to obtain a supported electrolyte; the supported electrolyte is then sintered at 800℃~1100℃.

[0010] S3. The supported electrolyte is impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2, and then sintered at 800℃~1100℃ to obtain a highly catalytically active air electrode.

[0011] Preferably, in S1, the CaFe is synthesized by at least one of the following methods: sol-gel method, solid-phase method, co-precipitation method, and hydrothermal method. 0.5 Al 0.25 Cu 0.25 O 3-δ Material.

[0012] Preferably, when the sol-gel method is used to synthesize CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ When processing materials, step S1 includes the following steps:

[0013] Add Ca(NO3)2·4H2O or Ca(NO3)2, Fe(NO3)3·9H2O or Fe(NO3)3, Al(NO3)3·9H2O or Al(NO3)3, Cu(NO3)2 to water, heat and mix until dissolved to obtain a mixed solution;

[0014] A first complexing agent, a second complexing agent, and a pH adjuster are added to the mixture to obtain a sol;

[0015] The sol was heated and mixed until the water was fully evaporated, turning into a gel. Then it was dried, calcined, and pulverized to obtain CaFe. 0.5 Al 0.25 Cu 0.25 O 3-δ Material.

[0016] Preferably, in S1, the first complexing agent is selected from one or more of ethylenediaminetetraacetic acid, aminotriacetic acid, and diethylenetriaminepentacarboxylate;

[0017] The second complexing agent is selected from one or more of citric acid, malic acid, and oxalic acid;

[0018] The pH adjuster is selected from one or more of ammonia, acetone, and ethanolamine;

[0019] The mass ratio of Ca(NO3)2·4H2O or Ca(NO3)2, Fe(NO3)3·9H2O or Fe(NO3)3, Al(NO3)3·9H2O or Al(NO3)3, Cu(NO3)2, the first complexing agent, and the second complexing agent is 23.615:20.2:9.378:4.689:54~62:80~88;

[0020] The drying temperature is 150℃~200℃, and the time is 4h~6h;

[0021] The firing temperature is 900℃~1100℃, and the firing time is 4h~6h.

[0022] Preferably, in S2, the electrolyte after acid treatment is an electrolyte treated with nitric acid with a mass fraction of 60% to 80%, wherein the acid treatment time is 5 min to 20 min, and the electrolyte includes at least one of BZCYYb electrolyte, YSZ electrolyte, SDC electrolyte, GDC electrolyte and LSGM electrolyte.

[0023] Preferably, in S2, the sintering time is 1h to 3h.

[0024] Preferably, in step S3, the concentration of the mixed salt solution is 0.1 mol / L to 1 mol / L, and the immersion time is 3 s to 10 s.

[0025] Preferably, in S3, the mass ratio of Fe(NO3)3 to Cu(NO3)2 is 1-2:1-2.

[0026] Preferably, in step S3, the sintering time is 4h to 6h.

[0027] A second aspect of the present invention provides a highly catalytically active air electrode, which is obtained by the preparation method described above.

[0028] A third aspect of the present invention provides a solid oxide fuel cell, including the air electrode described above.

[0029] A fourth aspect of the present invention provides a method for preparing a solid oxide fuel cell as described in the third aspect, wherein the solid oxide fuel cell is a symmetrical cell, and the method for preparing the solid oxide fuel cell includes the following steps:

[0030] NiO is added to electrolyte powder, pressed into shape, and calcined to obtain electrolyte.

[0031] The electrolyte is treated with acid to obtain an acid-treated electrolyte.

[0032] The synthesized CaFe 0.5 Al 0.25 Cu0.25 O 3-δ The material was mixed with isopropanol, ethylene glycol and glycerol, and ball-milled to obtain an air electrode slurry;

[0033] The air electrode slurry is loaded onto an acid-treated electrolyte and sintered at 800℃~1100℃. Then, it is impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 and sintered again at 800℃~1100℃ to obtain a symmetrical cell.

[0034] A fifth aspect of the present invention provides a method for preparing a solid oxide fuel cell as described in the third aspect, wherein the solid oxide fuel cell is a single cell, and the method for preparing the solid oxide fuel cell includes the following steps:

[0035] An anode is obtained by pressing the anode powder into a mold, wherein the anode powder includes NiO, electrolyte and starch;

[0036] An electrolyte is placed on the anode surface, pressed, and calcined to obtain a half-cell.

[0037] The electrolyte portion of the half-cell is treated with acid to obtain an acid-treated electrolyte.

[0038] The synthesized CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The material was mixed with isopropanol, ethylene glycol and glycerol, and ball-milled to obtain an air electrode slurry;

[0039] The air electrode slurry is loaded onto an acid-treated electrolyte and sintered at 800℃~1100℃. Then, it is impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 and sintered again at 800℃~1100℃ to obtain a single cell.

[0040] This invention has at least one of the following beneficial effects:

[0041] 1. In one aspect, this invention uses raw materials Ca, Fe, Al, and Cu to prepare CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The air electrode material does not contain precious metals or rare earth metals, but only uses common non-precious metals, thereby reducing production costs; compared with the widely used SOFC air electrode material BaCo in existing technologies. 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ In comparison, the air electrode CaFe of the present invention0.5 Al 0.25 Cu 0.25 O 3-δ Material costs were reduced by nearly 75%. On the other hand, due to the CaFe prepared above... 0.5 Al 0.25 Cu 0.25 O 3-δ The catalytic activity and polarization resistance of the material are not competitive in the market compared to classic materials containing noble metals and rare earth elements. This invention addresses this issue by modifying CaFe... 0.5 Al 0.25 Cu 0.25 O 3-δ The air electrode was optimized by methods such as electrode sintering temperature, acid treatment of the electrode-electrolyte interface, and electrode impregnation, which improved the catalytic activity of the air electrode and reduced the polarization resistance.

[0042] 2. The polarization impedance of the air electrode prepared using the method of this invention is 0.026 Ω / cm. 2 (750℃), the power density in a proton conductor fuel cell (PCFC) at 750℃ is 632 mW / cm³. 2 In an oxygen ion conductor fuel cell (SOFC), the power density at 850°C is 577 mW / cm³. 2 Considering both cost and performance, it possesses significant market competitiveness. Attached Figure Description

[0043] Figure 1 This is a flowchart illustrating the preparation process of the present invention.

[0044] Figure 2 Arrhenius plots of polarization impedance before and after CFAC optimization.

[0045] Figure 3 IV curves and power density plots before and after CFAC optimization.

[0046] Figure 4 SEM images of electrolyte surfaces after different acid treatment times.

[0047] Figure 5 The polarization impedance Arrhenius plots of CFAC at different impregnation times are shown.

[0048] Figure 6 SEM images of CFAC at different impregnation concentrations.

[0049] Figure 7 The images show the XRD patterns of CFAC before and after impregnation.

[0050] Figure 8The polarization impedance Arrhenius plots of CFAC before and after immersion in a 0.15 mol / L 1:1 Fe(NO3)3 and Cu(NO3)2 mixed salt solution are shown. Detailed Implementation

[0051] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0052] An embodiment of the present invention provides a method for preparing a highly catalytically active air electrode, comprising the following steps:

[0053] S1, Synthesis of CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ Materials, where 0 ≤ δ < 1;

[0054] S2, the CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The material is loaded onto an acid-treated electrolyte to obtain a supported electrolyte, which is then sintered at 800℃~1100℃.

[0055] S3. The supported electrolyte is impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 and sintered at 800℃~1100℃ to obtain a highly catalytically active air electrode.

[0056] This invention uses low-cost elements Ca, Fe, Al, and Cu to synthesize CaFe. 0.5 Al 0.25 Cu 0.25 O 3-δ (CFAC) material was used, thereby reducing costs; however, the catalytic activity and polarization resistance of this air electrode are not competitive in the market compared to classic materials containing noble metals and rare earth elements. Therefore, this invention further explored optimization strategies including sintering temperature optimization, acid treatment, and impregnation with low-cost salt solutions, successfully reducing the polarization resistance of the CFAC electrode and successfully improving the power output of the full cell based on this air electrode.

[0057] In some embodiments, S1, CaFe is synthesized. 0.5 Al 0.25 Cu 0.25 O 3-δ The methods for the materials include at least one of the following: sol-gel method, solid phase method, coprecipitation method and hydrothermal method.

[0058] In some embodiments, in S1, CaFe is synthesized using the sol-gel method. 0.5 Al 0.25 Cu 0.25 O 3-δ The material method includes the following steps:

[0059] Ca(NO3)2·4H2O or Ca(NO3)2, Fe(NO3)3·9H2O or Fe(NO3)3, Al(NO3)3·9H2O or Al(NO3)3, Cu(NO3)2 are heated and stirred in water until fully dissolved. Then, ethylenediaminetetraacetic acid, citric acid monohydrate, and ammonia are added to the solution. The resulting sol is heated and stirred until the water is fully evaporated, and the solution becomes a gel. The gel is dried and then calcined at high temperature. The calcined powder is then ground to obtain CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ Material.

[0060] In some embodiments, the first complexing agent is selected from one or more of ethylenediaminetetraacetic acid, aminotriacetic acid, and diethylenetriaminepentacarboxylate; the second complexing agent is selected from one or more of citric acid, malic acid, and oxalic acid; and the pH adjuster is selected from one or more of ammonia, acetone, and ethanolamine. Preferably, the first complexing agent is selected from ethylenediaminetetraacetic acid, the second complexing agent is selected from citric acid monohydrate, and the pH adjuster is selected from ammonia.

[0061] In some embodiments, the addition ratio of Ca(NO3)2·4H2O or Ca(NO3)2, Fe(NO3)3·9H2O or Fe(NO3)3, Al(NO3)3·9H2O or Al(NO3)3, Cu(NO3)2, the first complexing agent, the second complexing agent, and the pH adjuster is 23.615g:20.2g:9.378g:4.689g:54~62g:80~88:300~314mL; preferably 23.615g:20.2g:9.378g:4.689g:56~60g:305~310mL, specifically 23.615g:20.2g:9.378g:4.689g:58.448g:84.056g and 308.28ml.

[0062] In some embodiments, the drying temperature is 150℃~200℃ and the time is 4h~6h; preferably, the drying temperature is 160℃~190℃ and the time is 4.2h~5.8h; more preferably, the drying temperature is 170℃~180℃ and the time is 4.5h~5.5h; specifically, the drying temperature is 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃ and the time is 4h, 5h or 6h.

[0063] The high-temperature firing temperature is 900℃~1100℃, and the time is 4h~6h. Preferably, the high-temperature firing temperature is 950℃~1050℃, and the time is 4.2h~5.8h; more preferably, the high-temperature firing temperature is 980℃~1020℃, and the time is 4.5h~5.5h; specifically, the high-temperature firing temperature is 900℃, 950℃, 1000℃, 1050℃ or 1100℃, and the time is 4h, 5h or 6h.

[0064] In some embodiments, in S2, the acid treatment method involves treating the electrolyte with 60%–80% nitric acid by mass for 5–20 minutes, and employing ultrasound during the acid treatment process at a frequency of 30–50 Hz. Preferably, the acid is 65%–75% nitric acid by mass, the acid treatment time is 8–18 minutes, and the ultrasound frequency is 32–48 Hz; more preferably, the acid is 67%–73% nitric acid by mass, the acid treatment time is 8–15 minutes, and the ultrasound frequency is 35–45 Hz; specifically, the acid is 65%, 70%, or 75% nitric acid by mass, the acid treatment time is 5, 10, 15, or 20 minutes, and the ultrasound frequency is 40 Hz.

[0065] In some embodiments, in S2, the electrolyte includes one of BZCYYb electrolyte, YSZ electrolyte, SDC electrolyte, GDC electrolyte and LSGM electrolyte; the sintering time is 1h to 3h, preferably 1.5h to 2.5h, specifically 1h, 1.5h, 2h, 2.5h or 3h.

[0066] In some embodiments, in step S3, the concentration of the mixed salt solution is 0.1 mol / L to 1 mol / L, and the immersion time is 3 s to 10 s. Preferably, the concentration of the mixed salt solution is 0.2 mol / L to 0.8 mol / L, and the immersion time is 3 s to 8 s. More preferably, the concentration of the mixed salt solution is 0.3 mol / L to 0.5 mol / L, and the immersion time is 4 s to 7 s. Specifically, the concentration of the mixed salt solution is 0.1 mol / L, 0.25 mol / L, 0.4 mol / L, 0.5 mol / L, 0.8 mol / L, or 1 mol / L, and the immersion time is 3 s, 5 s, 6 s, 8 s, or 10 s.

[0067] In some embodiments, in S3, the mass ratio of Fe(NO3)3 to Cu(NO3)2 is 1-2:1-2, preferably 1-1.5:1-1.5, and more preferably 1-1.2:1-1.2. Specifically, it is 1:1, 1:1.5, 1:2, 1.5:1, 2:1.5, or 2:1, etc.

[0068] In some embodiments, in S3, the sintering time is 4h to 6h, preferably 4.2h to 5.8h; more preferably 4.5h to 5.5h; specifically 4h, 5h or 6h.

[0069] Another embodiment of the present invention provides a highly catalytically active air electrode, which is obtained by the above-described preparation method.

[0070] The polarization impedance of the air electrode prepared using the method of this invention is 0.026 Ω / cm. 2 (750℃), the power density in a proton conductor fuel cell (PCFC) at 750℃ is 632 mW / cm³. 2 In an oxygen ion conductor fuel cell (SOFC), the power density at 850°C is 577 mW / cm³. 2 Considering both cost and performance, it possesses significant market competitiveness.

[0071] Another embodiment of the present invention provides a solid oxide fuel cell, including the air electrode, electrolyte and anode described above.

[0072] The solid oxide fuel cell prepared by this invention has excellent electrochemical performance, low polarization impedance and excellent output power.

[0073] Another embodiment of the present invention provides a method for preparing a solid oxide fuel cell, wherein the solid oxide fuel cell is a symmetrical cell or a single cell, wherein...

[0074] The method for preparing the symmetrical battery includes the following steps:

[0075] NiO is added to electrolyte powder, pressed into shape, and calcined to obtain electrolyte.

[0076] The electrolyte is treated with acid to obtain an acid-treated electrolyte.

[0077] The synthesized CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The material was mixed with isopropanol, ethylene glycol and glycerol, and ball-milled to obtain an air electrode slurry;

[0078] The air electrode slurry is loaded onto an acid-treated electrolyte and sintered at 800℃~1100℃; then it is impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 and sintered again at 800℃~1100℃ to obtain a symmetrical cell.

[0079] The method for preparing the single cell includes the following steps:

[0080] The anode powder is pressed into shape to obtain the anode; wherein the anode powder includes NiO, electrolyte and starch;

[0081] An electrolyte is placed on the anode surface, pressed, and calcined to obtain a half-cell.

[0082] The electrolyte portion of the half-cell is treated with acid to obtain an acid-treated electrolyte.

[0083] The synthesized CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The material was mixed with isopropanol, ethylene glycol and glycerol, and ball-milled to obtain an air electrode slurry;

[0084] The air electrode slurry is sprayed onto the acid-treated electrolyte and sintered at 800℃~1100℃; then it is impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 and sintered again at 800℃~1100℃ to obtain a single cell.

[0085] In some embodiments, in the preparation method of the symmetrical battery, the amount of NiO added is 0.5-1.5% of the mass of the BZCYYb electrolyte powder, the pressing pressure is 3-5 MPa, and the calcination temperature is 1400-1500℃; CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The ratio of air electrode to isopropanol, ethylene glycol and glycerol is 0.8-1.2 g: 9-11 mL: 1.5-2.5 mL: 0.7-0.9 mL.

[0086] In some embodiments, in the preparation method of the single cell, the mass ratio of NiO, electrolyte powder, and starch is 5–7:3–5:0.8–1.2, and the pressing pressure is 3–5 MPa; the pressing pressure after the electrolyte is placed on the anode surface is 7–9 MPa, and the calcination temperature is 1400–1500 °C; CaFe 0.5 Al 0.25 Cu 0.25 O 3-δThe ratio of air electrode to isopropanol, ethylene glycol and glycerol is 0.8-1.2 g: 9-11 mL: 1.5-2.5 mL: 0.7-0.9 mL.

[0087] This invention is the first to propose using a sol-gel synthesis method to synthesize an all-non-noble metal perovskite solid oxide fuel cell air electrode based on Ca, Fe, Al, and Cu. The increased use of Al, in particular, further reduces material costs, and the performance, after optimization by this invention, still maintains a competitive edge in the market. The optimization methods mentioned in this invention include refining the air electrode sintering temperature, electrode-electrolyte interface-acid treatment, and electrode impregnation. This invention explores specific optimization parameters for each method, obtaining the most suitable CaFe... 0.5 Al 0.25 Cu 0.25 O 3-δ The optimized processes and parameters significantly improve performance and make the product competitive in the market.

[0088] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following specific embodiments.

[0089] Example 1

[0090] like Figure 1 As shown, this embodiment provides CaFe 0.5 Al 0.25 Cu 0.25 The synthesis and optimization methods for O3 include the following steps:

[0091] (1) Synthesis of CaFe by sol-gel method 0.5 Al 0.25 Cu 0.25 O3 (i.e., δ = 0) is synthesized using the following steps:

[0092] The original cathode material was prepared using the sol-gel method to synthesize 0.1 mol of CaFe. 0.5 Al 0.25 Cu 0.25 O 3-δFor example, 23.615g Ca(NO3)2·4H2O, 20.2g Fe(NO3)3·9H2O, 9.378g Al(NO3)3·9H2O, and 4.689g Cu(NO3)2 were heated and stirred in purified water until fully dissolved. Then, 58.448g ethylenediaminetetraacetic acid (EDTA), 84.056g citric acid monohydrate (CA), and 308.28ml ammonia water were added to the solution. The mixed sol was heated and stirred until the water was fully evaporated, and the solution became a gel. The gel was then placed in an oven at 180℃ and dried for 5 hours, then transferred to a muffle furnace at 1000℃ and calcined for 5 hours. The calcined powder was then ground to obtain the doped CaFe product. 0.5 Al 0.25 Cu 0.25 O3 air electrode powder.

[0093] (2) Preparation of symmetrical cells: 1% (1% of the mass of BZCYYb electrolyte powder) of NiO was mixed into BZCYYb electrolyte powder, and then 0.2g of electrolyte powder was pressed into round blocks and dry-pressed into round discs under a pressure of 4MPa in a tablet press, and calcined at 1450℃ to obtain a dense and smooth electrolyte.

[0094] 1g of the air electrode prepared in step (1) was mixed in 10ml isopropanol, 2ml ethylene glycol, and 0.8ml glycerol, and ball-milled for 40 minutes to obtain an air electrode slurry for spraying. The air electrode slurry was then sprayed onto both sides of the sintered electrolyte and calcined at 900℃ for 2 hours to obtain a symmetrical cell with the unoptimized CFAC air electrode.

[0095] (3) Preparation of single cells: Powder dry pressing process was adopted. The electrolyte was BZCYYb, and the anode was a mixed powder of NiO:BZCYYb:starch = 6:4:1 (mass ratio). 0.35g of anode powder was pressed into a round block under a pressure of 4MPa in a tablet press. Then, 0.02g of BZCYYb electrolyte was evenly spread on the anode surface and co-pressed under a pressure of 8MPa to obtain a half-cell green. Then, it was calcined in an air atmosphere at 1450℃ for 5 hours to obtain a prepared half-cell with a diameter of 12mm. The air electrode slurry prepared in step (1) was sprayed onto the electrolyte surface and calcined at 900℃ for 2 hours to fully combine the air electrode and the electrolyte. A complete single cell with an optimized CFAC air electrode was obtained.

[0096] This embodiment also provides the preparation of another single cell with YSZ electrolyte, which can be achieved by replacing BZCYYb with YSZ, while optimizing the method, parameters and process.

[0097] (4) CaFe 0.5 Al0.25 Cu 0.25 Optimization of O3 air electrode:

[0098] The dense and smooth BZCYYb electrolyte prepared in step (2) was treated with 70% nitric acid by ultrasound (frequency 40 Hz) for 10 min; the CaFe prepared in step (1) was then... 0.5 Al 0.25 Cu 0.25 O 3-δ Air electrode powder (CFAC) was loaded onto a dense and smooth BZCYYb electrolyte prepared in step (2) after ultrasonic treatment (frequency 40 Hz) with 70% nitric acid for 10 min. The electrolyte was then sintered at 900 °C for 2 h. Next, the CFAC air electrode was immersed in a mixed salt solution of 0.25 mol / L Fe(NO3)3 and Cu(NO3)2 at a mass ratio of 1:1 for 5 seconds. Finally, the immersed cathode was sintered at 900 °C for 5 h. A symmetrical cell with an optimized CFAC air electrode was obtained.

[0099] The same optimization method described above is used to optimize the single cell with the optimized CFAC air electrode prepared in step (3).

[0100] (5) Performance testing:

[0101] Polarization impedance was measured on symmetrical cells using an electrochemical workstation to obtain Arrhenius plots, and impedance performance analysis was performed on the air electrode. Current-voltage (IV) curves were measured on single cells, and the power output of the single cell with the air electrode was analyzed.

[0102] Example 2

[0103] The difference from Example 1 is that steps (1), (2), (3), and (5) are the same as in Example 1, but in step (4), the sintering temperature after the symmetrical battery is coated with an air electrode is changed from 900°C for 2 hours to 800°C, 1000°C, and 1100°C for 2 hours. The rest are the same as in Example 1.

[0104] Example 3

[0105] The difference from Example 1 is that steps (1), (2), (3), and (5) are the same as in Example 1, and the dense electrolyte obtained in step (4) is subjected to "sonication (frequency 40Hz) treatment with 70% nitric acid" for 5 min, 15 min, and 20 min, respectively. Everything else is the same as in Example 1.

[0106] Example 4

[0107] The difference from Example 1 is that steps (1), (2), (3), and (5) are the same as in Example 1. In step (4), the air electrode side is immersed in a mixed salt solution with a mass ratio of 1:1 Fe(NO3)3 and Cu(NO3)2. The concentration of the mixed salt solution is changed to 1 mol / L, 0.5 mol / L, and 0.1 mol / L, respectively. The rest is the same as in Example 1.

[0108] Comparative Example 1

[0109] The difference from Example 1 is that Comparative Example 1 only performed steps (1), (2), (3), and (5), without performing the optimization process (4), that is, the resulting CaFe was unoptimized. 0.5 Al 0.25 Cu 0.25 O3.

[0110] Comparative Example 2

[0111] The difference from Example 1 is that steps (1), (2), (3), and (5) are the same as in Example 1, but only "sintering" is performed in step (4) of the optimization process, with sintering temperatures of 800℃, 900℃, 1000℃, and 1100℃ respectively. The specific method of optimization in step (4) is as follows:

[0112] The CaFe prepared in step (1) of Example 1 0.5 Al 0.25 Cu 0.25 O3 air electrode powder (CFAC) was loaded onto the electrolyte BZCYYb prepared in step (2), and then sintered at 800℃, 900℃, 1000℃ and 1100℃ for 2 hours respectively to obtain the treated symmetrical cell with CFAC air electrode.

[0113] Comparative Example 3

[0114] The difference from Example 1 is that steps (1), (2), (3), and (5) are the same as in Example 1, but only "900℃ sintering + electrolyte acid treatment" was performed in step (4) optimization. The specific method of step (4) optimization is as follows:

[0115] The CaFe prepared in step (1) of Example 1 0.5 Al 0.25 Cu 0.25 O3 air electrode powder (CFAC) was loaded onto BZCYYb electrolyte that had been ultrasonically treated with 70% nitric acid for 10 min, and then sintered at 900 °C for 2 h to obtain the treated CFAC air electrode.

[0116] Tests and Results

[0117] (1) The polarization impedance and electrochemical performance of all CFAC air electrodes prepared in Examples 1-4 and all Comparative Examples 1-3 were tested, and the results are as follows:

[0118] like Figure 2 The results shown are the polarization impedance test results of the CFAC air electrodes prepared in Example 1 and Comparative Examples 2-3. Figure 2 In the examples, "900 sintering + electrolyte acid treatment + impregnation" corresponds to Example 1, "900 sintering + electrolyte acid treatment" corresponds to Example 3, and "800 sintering, 900 sintering, 1000 sintering, and 1100 sintering" correspond to Example 2. Figure 2 It can be seen that, compared with Comparative Examples 2 and 3, the CFAC prepared in Example 1 after sintering temperature optimization, electrolyte acid treatment and impregnation has the lowest polarization resistance, indicating that the three aspects of sintering temperature optimization, electrolyte acid treatment and impregnation treatment are more conducive to reducing polarization resistance. Furthermore, the polarization resistance of the CFAC prepared in Comparative Example 3 is lower than that in Comparative Example 2, indicating that two aspects of optimization are more conducive to reducing polarization resistance than one aspect of optimization.

[0119] Regarding single-cell power output, the CFAC cathode treated with the optimization measures of Example 1 and the unoptimized CFAC cathode of Comparative Example 1 were respectively loaded onto half-cells prepared by dry pressing in the same batch, and their electrochemical performance was tested. The results are as follows: Figure 3 As shown, where, Figure 3 In Figure (a), the electrochemical performance of CFAC prepared in Comparative Example 1 in a proton conductor system with BZCYYb as the electrolyte is shown. Figure 3 (b) shows the electrochemical performance of the CFAC prepared in Example 1 in a proton conductor system with BZCYYb as the electrolyte. Figure 3 (c) in the figure represents the electrochemical performance of CFAC prepared in Comparative Example 1 in an oxygen ion conductor system with YSZ as the electrolyte. Figure 3 In Figure (d), the electrochemical performance of CFAC prepared in Example 1 in the oxygen ion conductor system with YSZ as the electrolyte is shown. Figure 3 It can be seen that in the proton conductor system with BZCYYb as the electrolyte, the power density increased by 19.7% after optimization (from 528 to 632 mW / cm²). 2 In the oxygen ion conductor system with YSZ as the electrolyte, the optimized power density increased by 52.2% (from 379 to 577 mW / cm²). 2 ).

[0120] The polarization impedance and output power of the CFAC before and after optimization were compared with those of the classic commercial cathode LSM. The results are shown in Table 1. Optimized CaFe 0.5 Al 0.25Cu 0.25 O 3-δ The cathode polarization impedance was reduced by 72.4%. Power was increased by 19.7% (protons) and 52.5% (oxygen ions), making it competitive with commercially available air electrodes (LSMs).

[0121] Table 1. Performance comparison between CFAC and LSM before and after optimization

[0122]

[0123] Examples 2-4 investigated the effects of sintering temperature, electrolyte surface acid treatment time, and salt solution impregnation concentration on CFAC, and the results are as follows:

[0124] 1) Sintering temperature

[0125] The electrode-electrolyte interface is crucial for the overall battery impedance. Air electrodes are often bonded to the electrolyte surface via high-temperature sintering. Different sintering temperatures have a significant impact on this. This invention explores the changes in polarization impedance of the air electrode at four sintering temperatures: 800℃, 900℃, 1000℃, and 1100℃. Figure 2 As shown, 900℃ was ultimately determined to be the optimal sintering temperature, which minimizes the polarization resistance of the symmetrical cell.

[0126] 2) Acid treatment of electrolyte surface

[0127] Studies have shown that acid treatment increases the surface roughness of the electrolyte, which significantly optimizes the contact between the air electrode and the electrolyte, thereby reducing battery impedance and improving performance.

[0128] The sintering between different cathodes and electrolytes is affected by the elemental properties of the material; therefore, there exists an electrolyte roughness most suitable for this material's CFAC. This invention, by optimizing the acid treatment time and through roughness observation and characterization, obtained the optimal suitable CaFe... 0.5 Al 0.25 Cu 0.25 O 3-δ The parameters in contact with the electrolyte further reduce the impedance during battery testing.

[0129] This invention uses a 70% nitric acid titration solution to immerse the electrolyte in nitric acid and then sonicate it. The main focus is on exploring the sonication time of the nitric acid, including 5 min, 10 min, 15 min, and 20 min. Morphological observation is then used to determine the acid content. Figure 4 Initially, 10 min and 15 min were selected as alternatives. Then, the cathode was loaded onto the electrolyte treated for 10 min and 15 min respectively, and impedance tests were performed. Figure 5Finally, the electrolyte with a treatment time of 10 minutes was selected as the most suitable, as it has the lowest polarization resistance.

[0130] 3) Electrode impregnation

[0131] To further optimize the performance of the air electrode CFAC of this invention, based on the optimization of sintering temperature and electrolyte treatment, this invention further incorporates CaFe... 0.5 Al 0.25 Cu 0.25 O 3-δ The surface of the air electrode was impregnated with a low-cost salt solution.

[0132] The impregnation salt solution was a 1:1 mass mixture of Fe(NO3)3 and Cu(NO3)2 in deionized water. This invention also explored the effects of different concentrations of this mixed salt solution on the CFAC cathode. This included exploring the impregnation effects based on four concentrations of salt solutions: 1 mol / L, 0.5 mol / L, 0.25 mol / L, and 0.1 mol / L.

[0133] The specific operating procedure is as follows: The cathode portion of the battery with the prepared and sintered CFAC air electrode is immersed in salt solutions of different concentrations for 5 seconds, and then sintered at 900℃ for 5 hours to obtain the finished product. The surface of the CFAC after immersion in salt solutions of different concentrations is observed, and the results are as follows. Figure 6 As shown. Ultimately, this invention concludes that the CFAC air electrode impregnated in a mixed salt solution of 0.25 mol / L Fe(NO3)3 and Cu(NO3)2 with a mass ratio of 1:1 yields the best impregnation effect and the most suitable particle distribution on the electrode surface.

[0134] Figure 7 XRD results showed that the micro / nanoparticles on the impregnation surface were metal oxides of Fe₂O₃ and CuO. Polarization impedance measurements were performed as follows... Figure 8 As shown, the CFAC impedance was reduced under this impregnation effect.

[0135] (2) Cost-price comparison

[0136] From the perspective of material costs, CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ Compared to other high-performance cathode materials (BCFZY), the material cost is reduced by approximately 75%. For example, the latest international rare earth prices are shown in Table 2 below.

[0137] Table 2. Price comparison of common rare elements in air electrodes and non-precious metals used in this invention (RMB 10,000 / ton)

[0138]

[0139] Based on the price data in Table 2:

[0140] This invention prepares one ton of CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The material cost of the air electrode is 41,295 yuan, while one ton of BaCo... 0.4 Fe 0.4 Zr 0.1 Y 0.1 The material cost of the O3 air electrode is 166,364 yuan, and the material cost of the present invention is reduced by 75.18%.

[0141] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a highly catalytically active air electrode, characterized in that, Includes the following steps: S1, Synthesis of CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ Materials, where 0 ≤ δ < 1; S2, the CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The material is loaded onto the acid-treated electrolyte to obtain a supported electrolyte, which is then sintered at 800℃~1100℃. S3. The supported electrolyte is impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2, and then sintered at 800℃~1100℃ to obtain a highly catalytically active air electrode.

2. The preparation method according to claim 1, characterized in that, The CaFe was synthesized by at least one of the following methods: sol-gel method, solid-phase method, coprecipitation method, and hydrothermal method. 0.5 Al 0.25 Cu 0.25 O 3-δ Material.

3. The preparation method according to claim 2, characterized in that, When the sol-gel method is used to synthesize CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ When processing materials, step S1 includes the following steps: Add Ca(NO3)2·4H2O or Ca(NO3)2, Fe(NO3)3·9H2O or Fe(NO3)3, Al(NO3)3·9H2O or Al(NO3)3, Cu(NO3)2 to water, heat and mix until dissolved to obtain a mixed solution; A first complexing agent, a second complexing agent, and a pH adjuster are added to the mixture to obtain a sol; The sol was heated and mixed until the water evaporated, turning into a gel. Then it was dried, calcined, and pulverized to obtain CaFe. 0.5 Al 0.25 Cu 0.25 O 3-δ Material.

4. The preparation method according to claim 3, characterized in that, In S1, The first complexing agent is selected from one or more of ethylenediaminetetraacetic acid, aminotriacetic acid, and diethylenetriaminepentacarboxylic acid. The second complexing agent is selected from one or more of citric acid, malic acid, and oxalic acid; The pH adjuster is selected from one or more of ammonia, acetone, and ethanolamine; The mass ratio of Ca(NO3)2·4H2O or Ca(NO3)2, Fe(NO3)3·9H2O or Fe(NO3)3, Al(NO3)3·9H2O or Al(NO3)3, Cu(NO3)2, the first complexing agent, and the second complexing agent is 23.615:20.2:9.378:4.689:54~62:80~88; The drying temperature is 150℃~200℃, and the time is 4h~6h; The firing temperature is 900℃~1100℃, and the firing time is 4h~6h.

5. The preparation method according to claim 1, characterized in that, In S2, The electrolyte after acid treatment is an electrolyte treated with 60% to 80% nitric acid by mass, wherein the acid treatment time is 5 min to 20 min, and the electrolyte includes at least one of BZCYYb electrolyte, YSZ electrolyte, SDC electrolyte, GDC electrolyte and LSGM electrolyte; The sintering time is 1 hour to 3 hours.

6. The preparation method according to claim 1, characterized in that, In S3, The concentration of the mixed salt solution is 0.1 mol / L to 1 mol / L, and the immersion time is 3 s to 10 s; The mass ratio of Fe(NO3)3 to Cu(NO3)2 is 1-2:1-2; The sintering time is 4h to 6h.

7. A highly catalytically active air electrode, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 6.

8. A solid oxide fuel cell, characterized in that, Includes the air electrode as described in claim 7.

9. A method for preparing a solid oxide fuel cell as described in claim 8, characterized in that, The solid oxide fuel cell is a symmetrical cell, and the preparation method of the solid oxide fuel cell includes the following steps: NiO is added to electrolyte powder, pressed into shape, and calcined to obtain electrolyte. The electrolyte is treated with acid to obtain an acid-treated electrolyte. The synthesized CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The material was mixed with isopropanol, ethylene glycol and glycerol, and ball-milled to obtain an air electrode slurry; The air electrode slurry is loaded onto an acid-treated electrolyte and sintered at 800℃~1100℃. Then, it is impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 and sintered again at 800℃~1100℃ to obtain a symmetrical cell.

10. A method for preparing a solid oxide fuel cell as described in claim 8, characterized in that, The solid oxide fuel cell is a single cell, and the preparation method of the solid oxide fuel cell includes the following steps: The anode powder is pressed into shape to obtain the anode, wherein the anode powder includes NiO, electrolyte and starch; An electrolyte is placed on the anode surface, pressed, and calcined to obtain a half-cell. The electrolyte portion of the half-cell is treated with acid to obtain an acid-treated electrolyte. The synthesized CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The material was mixed with isopropanol, ethylene glycol and glycerol, and ball-milled to obtain an air electrode slurry; The air electrode slurry is loaded onto an acid-treated electrolyte and sintered at 800℃~1100℃. Then, it is impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 and sintered again at 800℃~1100℃ to obtain a single cell.

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