High-catalytic-activity air electrode, preparation method thereof and solid oxide fuel cell

Abstract

The invention discloses a high-catalytic-activity air electrode, a preparation method thereof and a solid oxide fuel cell, and relates to the technical field of cells. The preparation method of the air electrode comprises the following steps: synthesizing a CaFe0. 5Al0. 25Cu0. 25O3-delta material, wherein delta is more than or equal to 0 and less than 1; the method comprises the following steps: loading a CaFe < 0.5 > Al < 0.25 > Cu < 0.25 > O < 3-delta > material on an electrolyte subjected to acid treatment, and sintering at 800 DEG C to 1100 DEG C; and dipping by adopting a mixed salt solution containing Fe (NO3) 3 and Cu (NO3) 2, and continuously sintering at 800-1100 DEG C to obtain the composite material. The invention also provides a solid oxide fuel cell comprising the air electrode. The preparation method has the beneficial effects that the CaFe < 0.5 > Al < 0.25 > Cu < 0.25 > O < 3-delta > material is prepared from low-cost non-noble metal and non-rare earth element raw materials, so that the production cost is reduced; the CaFe < 0.5 > Al < 0.25 > Cu < 0.25 > O < 3-delta > material is subjected to optimization treatment, so that the catalytic activity is improved, and the polarization impedance is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a high catalytic activity air electrode, a preparation method thereof, and a solid oxide fuel cell. Background Art

[0002] A solid oxide fuel cell (SOFC) is a fully solid-state chemical power generation device that directly and efficiently converts the chemical energy stored in fuels and oxidants into electrical energy in an environmentally friendly manner at medium and 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 to oxygen ions and enabling effective charge transfer at the electrolyte interface.

[0003] At present, there are many high-performance air electrode materials, but almost all high-performance air electrodes 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 O5 and other high-performance air electrode materials. The high material cost has become an important factor restricting the development and industrialization of SOFCs. There is a need for an air electrode synthesized using only common non-precious metal elements (such as Ca, Fe, Al, Cu, etc.) without relying 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 still needed to improve their catalytic activity. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a high catalytic activity air electrode, a preparation method thereof, and a solid oxide fuel cell. On the one hand, the present invention uses 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 the production cost; on the other hand, by 0.5 Al 0.25 Cu 0.25 O 3-δThe air electrode is optimized to improve its catalytic activity and reduce the polarization impedance.

[0005] In the present invention, a low-cost composite perovskite-type air electrode CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ (0 < δ < 1) is synthesized by the sol-gel method. This cathode does not contain noble metals and rare earth metals, but only common non-noble metals. Compared with the currently widely used SOFC air electrode material BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ reported in Science (2015), the material cost of the air electrode CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ (CFAC) is reduced by nearly 75%. Moreover, the catalytic activity and polarization impedance of CFAC prepared only by the sol-gel method are not competitive in the market compared with the classical materials containing noble metals and rare earth elements. In the present invention, CFAC is improved and optimized by exploring and optimizing the electrode sintering temperature, acid treatment of the electrode-electrolyte interface, electrode impregnation, etc., successfully reducing the polarization impedance of CFAC and successfully improving the power output of the full cell based on this air electrode. Finally, the polarization impedance of the optimized air electrode is 0.026 Ω / cm 2 (750 °C), and the power density at 750 °C is 632 mW / cm 2 in the proton conductor fuel cell (PCFC), and the power density at 850 °C is 577 mW / cm 2 in the oxygen ion conductor fuel cell (SOFC), showing obvious market competitiveness in terms of both cost and performance.

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

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

[0008] S1. Synthesize CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material, where 0 ≤ δ < 1;

[0009] S2. Mix the CaFe 0.5 Al 0.25 Cu 0.25 O 3-δThe material is loaded onto the acid-treated electrolyte to obtain a supported electrolyte; the supported electrolyte is sintered at 800°C to 1100°C;

[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°C to 1100°C to obtain a highly catalytically active air electrode.

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

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

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

[0014] A first complexing agent, a second complexing agent, and a pH regulator are added to the mixed solution to obtain a sol;

[0015] The sol is heated and mixed until the water is fully evaporated and becomes gel-like, then dried, fired, 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, nitrilotriacetic acid, and diethylenetriaminepenta-carboxylate;

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

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

[0019] The mass ratio of the added 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 °C to 200 °C, and the time is 4 h to 6 h;

[0021] The firing temperature is 900 °C to 1100 °C, and the time is 4 h to 6 h.

[0022] Preferably, in S2, the electrolyte after acid treatment is the electrolyte treated with nitric acid having a mass fraction of 60% - 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 1 h to 3 h.

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

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

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

[0027] The second aspect of the present invention provides a high catalytic activity air electrode obtained by the above preparation method.

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

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

[0030] Add NiO to the electrolyte powder, press and mold, and calcine to obtain the electrolyte;

[0031] Treat the electrolyte with acid to obtain the acid-treated electrolyte;

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

[0033] The air electrode slurry is loaded on the acid-treated electrolyte and sintered at 800°C to 1100°C, and then impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2, and sintered continuously at 800°C to 1100°C to obtain a symmetrical cell.

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

[0035] The anode powder is pressed into shape to obtain an anode, wherein the anode powder includes NiO, electrolyte and starch;

[0036] The electrolyte is disposed on the surface of the anode, pressed and calcined to obtain a half cell;

[0037] The electrolyte part 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 is mixed with isopropanol, ethylene glycol and glycerol and ball-milled to obtain an air electrode slurry;

[0039] The air electrode slurry is loaded on the acid-treated electrolyte and sintered at 800°C to 1100°C, and then impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2, and sintered continuously at 800°C to 1100°C to obtain a single cell.

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

[0041] 1. On the one hand, the present invention uses raw materials Ca, Fe, Al, and Cu to prepare CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ air electrode material. This air electrode material does not contain precious metals and rare earth metals, and only uses common non-precious metals, thereby reducing production costs; compared with the SOFC air electrode material BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ used widely in the prior art, the air electrode CaFe of the present invention0.5 Aluminum 0.25 Copper 0.25 Oxygen 3-δ The material cost is reduced by nearly 75%. On the other hand, due to the above-prepared CaFe 0.5 Aluminum 0.25 Copper 0.25 Oxygen 3-δ The catalytic activity and polarization impedance of the material are not competitive in the market compared with the classical materials containing noble metals and rare earth elements. In the present invention, the air electrode of CaFe 0.5 Aluminum 0.25 Copper 0.25 Oxygen 3-δ is optimized by means of electrode sintering temperature, acid treatment of the electrode-electrolyte interface, and electrode impregnation, etc., so as to improve the catalytic activity of the air electrode and reduce the polarization impedance.

[0042] 2. The polarization impedance of the air electrode prepared by optimizing with the method of the present invention is 0.026 Ω / cm 2 (750 °C), and the power density at 750 °C in a proton conductor fuel cell (PCFC) is 632 mW / cm 2 , and the power density at 850 °C in an oxygen ion conductor fuel cell (SOFC) is 577 mW / cm 2 , which has obvious market competitiveness considering both cost and performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is the preparation flow chart of the present invention.

[0044] Figure 2 is the Arrhenius diagram of the polarization impedance of CFAC before and after optimization.

[0045] Figure 3 is the I-V curve and power density diagram of CFAC before and after optimization.

[0046] Figure 4 is the SEM diagram of the electrolyte surface at different acid treatment times.

[0047] Figure 5 is the Arrhenius diagram of the polarization impedance of CFAC at different impregnation times.

[0048] Figure 6 is the SEM diagram of CFAC at different impregnation concentrations.

[0049] Figure 7 is the XRD diagram of CFAC before and after impregnation.

[0050] Figure 8Arrhenius plots of the polarization resistance of CFAC before and after impregnation with a 1:1 mixed salt solution of Fe(NO3)3 and Cu(NO3)2 at 0.15 mol / L. Detailed implementation mode

[0051] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present 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 only used to explain the present invention and are not used to limit the present invention.

[0052] An embodiment of the present invention provides a method for preparing a high-catalytic-activity air electrode, including the following steps:

[0053] S1. Synthesize CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material, where 0 ≤ δ < 1;

[0054] S2. Load the CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material on the acid-treated electrolyte to obtain a loaded electrolyte, and then sinter the loaded electrolyte at 800 °C to 1100 °C;

[0055] S3. Impregnate the loaded electrolyte with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2, and sinter at 800 °C to 1100 °C to obtain a high-catalytic-activity air electrode.

[0056] The present invention selects low-cost elements Ca, Fe, Al, and Cu to synthesize CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ (CFAC) material, thereby reducing the cost; however, since the catalytic activity and polarization resistance of this air electrode are not competitive in the market compared with classical materials containing precious metals and rare earth elements. Therefore, after further exploring optimization strategies including sintering temperature optimization, acid treatment, and impregnation with low-cost salt solutions, the present invention successfully reduces the polarization resistance of the CFAC electrode and successfully improves the power output of the full cell based on this air electrode.

[0057] In some embodiments, in S1, the method for synthesizing the CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material includes at least one of the sol-gel method, the solid-phase method, the co-precipitation method, and the hydrothermal method.

[0058] In some embodiments, in S1, the CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material method includes the following steps:

[0059] Heat and stir 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 in water. After complete dissolution, add ethylenediaminetetraacetic acid, citric acid monohydrate, and ammonia water to the solution. Heat and stir the mixed sol until the water is fully evaporated and the solution becomes gel-like; dry the gel, then calcine it at high temperature, and grind the calcined agglomerated powder 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, nitrilotriacetic acid, and diethylenetriaminepentaacetic acid; the second complexing agent is selected from one or more of citric acid, malic acid, and oxalic acid; the pH regulator is selected from one or more of ammonia water, 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 regulator is selected from ammonia water.

[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 regulator is 23.615 g: 20.2 g: 9.378 g: 4.689 g: 54 - 62 g: 80 - 88: 300 - 314 mL; preferably 23.615 g: 20.2 g: 9.378 g: 4.689 g: 56 - 60 g: 305 - 310 mL, specifically 23.615 g: 20.2 g: 9.378 g: 4.689 g: 58.448 g: 84.056 g, and 308.28 ml.

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

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

[0064] In some embodiments, in S2, the acid treatment method is to treat the electrolyte with nitric acid having a mass fraction of 60% to 80%, the acid treatment time is 5 min to 20 min, and ultrasound is used during the acid treatment, and the frequency of the ultrasound is 30 Hz to 50 Hz. Preferably, the acid is nitric acid having a mass fraction of 65% to 75%, the acid treatment time is 8 min to 18 min, and the frequency of the ultrasound is 32 Hz to 48 Hz; more preferably, the acid is nitric acid having a mass fraction of 67% to 73%, the acid treatment time is 8 min to 15 min, and the frequency of the ultrasound is 35 Hz to 45 Hz; specifically, the acid is nitric acid having a mass fraction of 65%, 70% or 75%, the acid treatment time is 5 min, 10 min, 15 min or 20 min, and the frequency of the ultrasound 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 1 h to 3 h, preferably 1.5 h to 2.5 h, specifically 1 h, 1.5 h, 2 h, 2.5 h or 3 h.

[0066] In some embodiments, in S3, the concentration of the mixed salt solution is 0.1 mol / L to 1 mol / L and the impregnation 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 impregnation 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 impregnation 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 impregnation 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, more preferably 1-1.2:1-1.2. Specifically, it can be 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 4 h to 6 h, preferably 4.2 h to 5.8 h; more preferably 4.5 h to 5.5 h; specifically, it can be 4 h, 5 h, or 6 h.

[0069] Another embodiment of the present invention provides a highly catalytically active air electrode obtained by using the above preparation method.

[0070] The polarization impedance of the air electrode prepared by optimizing the method of the present invention is 0.026 Ω / cm 2 (750 °C), and the power density at 750 °C in a proton conductor fuel cell (PCFC) is 632 mW / cm 2 , and the power density at 850 °C in an oxygen ion conductor fuel cell (SOFC) is 577 mW / cm 2 , which has obvious market competitiveness in terms of cost and performance.

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

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

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

[0074] The preparation method of the symmetrical cell includes the following steps:

[0075] Add NiO to the electrolyte powder, press and mold it, and calcine it to obtain the electrolyte;

[0076] Treat the electrolyte with acid to obtain the acid-treated electrolyte;

[0077] Mix the synthesized CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material with isopropanol, ethylene glycol, and glycerol, and ball mill it to obtain the air electrode slurry;

[0078] Load the air electrode slurry onto the acid-treated electrolyte and sinter at 800 °C to 1100 °C; then impregnate with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 and continue sintering at 800 °C to 1100 °C to obtain a symmetric cell.

[0079] The preparation method of the single cell includes the following steps:

[0080] Press the anode powder into a mold to obtain an anode; wherein, the anode powder includes NiO, electrolyte and starch;

[0081] Set the electrolyte on the surface of the anode, press and calcine to obtain a half cell;

[0082] Treat the electrolyte part of the half cell with acid to obtain the acid-treated electrolyte;

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

[0084] Spray the air electrode slurry onto the acid-treated electrolyte and sinter at 800 °C to 1100 °C; then impregnate with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2 and continue sintering at 800 °C to 1100 °C to obtain a single cell.

[0085] In some embodiments, in the preparation method of the symmetric cell, the addition amount of NiO is 0.5 to 1.5% of the mass of the BZCYYb electrolyte powder, the pressure for pressing into a mold is 3 to 5 MPa, and the calcination temperature is 1400 to 1500 °C; CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ The addition ratio of the air electrode to isopropanol, ethylene glycol and glycerol is 0.8 to 1.2 g: 9 to 11 mL: 1.5 to 2.5 mL: 0.7 to 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 to 7: 3 to 5: 0.8 to 1.2, the pressure for pressing into a mold is 3 to 5 MPa; the pressure for pressing after setting the electrolyte on the surface of the anode is 7 to 9 MPa, and the calcination temperature is 1400 to 1500 °C; CaFe 0.5 Al 0.25 Cu 0.25 O 3-δThe addition ratio of the air electrode, 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] The present invention first proposes to use the sol - gel synthesis method for synthesizing the air electrode of a fully non - noble metal perovskite solid oxide fuel cell based on Ca, Fe, Al, and Cu. In particular, the addition of Al further reduces the material cost, and after being optimized by the present invention, the performance still has a market competitive advantage. The optimization methods mentioned in the present invention include refining the sintering temperature of the air electrode, electrode - electrolyte interface - acid treatment, electrode impregnation, etc. The present invention explores specific optimization parameters based on each method and obtains the optimization process and parameters for CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ which greatly improve the performance and make it competitive in the market.

[0088] The following uses specific examples to further elaborate on the present invention in detail, but the present invention is not limited to the following specific examples.

[0089] Example 1

[0090] As Figure 1 shown, this example provides a synthesis method and an optimization treatment method for CaFe 0.5 Al 0.25 Cu 0.25 O3, including the following steps:

[0091] (1) Synthesize CaFe 0.5 Al 0.25 Cu 0.25 O3 (i.e., δ = 0) by the sol - gel method. The synthesis method includes the following steps:

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

[0093] (2) Preparation of the symmetrical cell: 1% (1% of the mass of the BZCYYb electrolyte powder) of NiO was mixed in the BZCYYb electrolyte powder. Then, 0.2 g of the electrolyte powder was dry-pressed into a circular tablet under a pressure of 4 MPa using a tablet press and calcined at 1450 °C to obtain a dense and smooth electrolyte.

[0094] 1 g of the air electrode prepared in step (1) was mixed in 10 ml of isopropanol, 2 ml of ethylene glycol, and 0.8 ml of glycerol, and ball-milled for 40 minutes to obtain an air electrode slurry for spray gun spraying. Then the air electrode slurry was sprayed on both sides of the sintered electrolyte and calcined at 900 °C for 2 hours to obtain a symmetrical cell with a CFAC air electrode before optimization treatment.

[0095] (3) Preparation of the single cell: The powder dry-pressing process was adopted. BZCYYb was used as the electrolyte, and a mixed powder of NiO:BZCYYb:starch = 6:4:1 (mass ratio) was used as the anode. 0.35 g of the anode powder was dry-pressed into a circular tablet under a pressure of 4 MPa using a tablet press. Then, 0.02 g of BZCYYb electrolyte was evenly spread on the surface of the anode, and co-pressed under a pressure of 8 MPa to obtain a green body of the half cell. Then, it was calcined in a muffle furnace at 1450 °C for 5 hours in an air atmosphere to obtain a prepared half cell with a diameter of 12 mm. The air electrode slurry prepared in step (1) was sprayed on the surface of the electrolyte and calcined at 900 °C for 2 hours to ensure full combination of the air electrode and the electrolyte. A complete single cell with a CFAC air electrode before optimization treatment was obtained.

[0096] This example also provides the preparation of another single cell with YSZ electrolyte. Just replace the above BZCYYb with YSZ, and the optimization method, parameters, and process remain unchanged.

[0097] (4) CaFe 0.5 Al0.25 Cu 0.25 Optimization treatment of CuO3 air electrode:

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

[0099] Using the same optimization method as above, a single cell with an optimized CFAC air electrode prepared in step (3) was obtained.

[0100] (5) Performance test:

[0101] The symmetrical cell was tested for polarization impedance using an electrochemical workstation to obtain an Arrhenius plot, and the impedance performance of the air electrode was analyzed. The single cell was tested for current-voltage (I-V) curve, and the power output of the single cell under this 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. In step (4), the sintering temperature after spraying the air electrode on the symmetrical cell was changed from calcining at 900 °C for 2 hours to calcining at 800 °C, 1000 °C, and 1100 °C for 2 hours. Others 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. In step (4), the time of "ultrasonic treatment with 70% nitric acid (frequency 40 Hz)" for the obtained dense electrolyte was 5 min, 15 min, and 20 min respectively. Others are the same as in Example 1.

[0106] Example 4

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

[0108] Comparative Example 1

[0109] The difference from Example 1 is as follows: Comparative Example 1 only performs steps (1), (2), (3), and (5), and does not perform the optimization treatment in (4), that is, the unoptimized CaFe 0.5 Al 0.25 Cu 0.25 O3 is obtained.

[0110] Comparative Example 2

[0111] The difference from Example 1 is as follows: Steps (1), (2), (3), and (5) are the same as those in Example 1. In the optimization treatment of step (4), only "sintering" is performed, and the sintering temperatures are 800 °C, 900 °C, 1000 °C, and 1100 °C respectively. The specific method of the optimization treatment in step (4) is as follows:

[0112] Load the CaFe 0.5 Al 0.25 Cu 0.25 O3 air electrode powder (CFAC) prepared in step (1) of Example 1 on the electrolyte BZCYYb prepared in step (2), and then sinter at 800 °C, 900 °C, 1000 °C, and 1100 °C for 2 hours respectively to obtain a processed symmetric cell with a CFAC air electrode.

[0113] Comparative Example 3

[0114] The difference from Example 1 is as follows: Steps (1), (2), (3), and (5) are the same as those in Example 1. In the optimization treatment of step (4), only "sintering at 900 °C + acid treatment of the electrolyte" is performed. The specific method of the optimization treatment in step (4) is as follows:

[0115] Load the CaFe 0.5 Al 0.25 Cu 0.25 O3 air electrode powder (CFAC) prepared in step (1) of Example 1 on the BZCYYb electrolyte after ultrasonic treatment with 70% nitric acid for 10 min, and then sinter at 900 °C for 2 hours respectively to obtain the processed CFAC air electrode.

[0116] Tests and Results

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

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

[0119] In terms of the single - cell power output, the CFAC cathode after being treated with the optimization measures of Example 1 and the unoptimized CFAC cathode of Comparative Example 1 were respectively loaded on the same batch of half - cells prepared by dry pressing for electrochemical performance testing. The results are as Figure 3 shown, among which, Figure 3 (a) is the electrochemical performance of the CFAC prepared in Comparative Example 1 in the proton - conductor system with BZCYYb as the electrolyte, Figure 3 (b) is the electrochemical performance of the CFAC prepared in Example 1 in the proton - conductor system with BZCYYb as the electrolyte, Figure 3 (c) is the electrochemical performance of the CFAC prepared in Comparative Example 1 in the oxygen - ion - conductor system with YSZ as the electrolyte, Figure 3 (d) is the electrochemical performance of the CFAC prepared in Example 1 in the oxygen - ion - conductor system with YSZ as the electrolyte. It can be Figure 3 seen that in the proton - conductor system with BZCYYb as the electrolyte, the power density after optimization increased by 19.7% (from 528 to 632 mW / cm 2 ); in the oxygen - ion - conductor system with YSZ as the electrolyte, the power density after optimization increased by 52.2% (from 379 to 577 mW / cm 2 ).

[0120] The polarization impedance and output power of the CFAC before and after optimization were compared with the market - classic commercial cathode LSM, and the results are shown in Table 1. The optimized CaFe 0.5 Al 0.25Cu 0.25 O 3-δ The cathodic polarization impedance is reduced by 72.4%. The power is increased by 19.7% (protons) and 52.5% (oxygen ions), which is competitive in the market compared with the commercial air electrode LSM.

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

[0122]

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

[0124] 1) Sintering temperature

[0125] The bonding at the electrode-electrolyte interface is very important for the impedance of the entire battery. The air electrode is often bonded to the surface of the electrolyte by high-temperature sintering. Different sintering temperatures have a great influence on this. In this invention, the change of the polarization impedance of this air electrode at four sintering temperatures of 800 °C, 900 °C, 1000 °C, and 1100 °C was explored as Figure 2 shown, and finally 900 °C was determined as the optimal sintering temperature, which can make the polarization impedance of the symmetrical battery the lowest.

[0126] 2) Acid treatment on the surface of the electrolyte

[0127] Research shows that after the surface of the electrolyte is acid-treated, the roughness increases, which will significantly optimize the contact between the air electrode and the electrolyte, thereby reducing the impedance of the battery and improving the performance.

[0128] The sintering between different cathodes and electrolytes is affected by material elements, so there is an optimal electrolyte roughness suitable for this material CFAC. In this invention, by optimizing the acid treatment time and through roughness observation and characterization, the optimal parameters for CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ in contact with the electrolyte were obtained to further reduce the impedance under battery testing.

[0129] The acid used in this invention is a 70% nitric acid titrant solution. The electrolyte is impregnated in nitric acid and ultrasonically treated. The main exploration is the time of ultrasonic treatment with nitric acid, including 5 min, 10 min, 15 min, and 20 min. Through morphology observation ( Figure 4 ), 10 min and 15 min were initially selected as alternatives. Then the cathode was respectively loaded on the electrolyte treated for 10 min and the electrolyte treated for 15 min for impedance testing ( Figure 5) Finally, the electrolyte under a treatment time of 10 minutes was selected as the most suitable one, with the lowest polarization impedance.

[0130] 3) Electrode impregnation

[0131] In order to further optimize the performance of the air electrode CFAC of the present invention, on the basis of optimizing the sintering temperature and electrolyte treatment, the present invention further impregnated the surface of the CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ air electrode with a low-cost salt solution.

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

[0133] The specific operation process was as follows: The cathode part of the battery with the prepared and sintered CFAC air electrode was impregnated in salt solutions of different concentrations for 5 seconds, and then sintered at 900 °C for 5 hours to obtain the finished product. Observe the surface of the CFAC after impregnation with salt solutions of different concentrations, and the results are as Figure 6 shown. Finally, the present invention believes that the CFAC air electrode impregnated with a 0.25 mol / L mixed salt solution of Fe(NO3)3 and Cu(NO3)2 with a mass ratio of 1:1 has the best impregnation effect, and the particle distribution attached to the electrode surface is the most suitable.

[0134] Figure 7 The XRD results of Figure 8 showed that the impregnated micro-nano particles were metal oxides of Fe2O3 and CuO. The polarization impedance test was as

[0135] (2) Cost price comparison

[0136] In terms of material cost, CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ compared with other high-performance cathode materials (BCFZY), the material cost was reduced by ~75%. Taking the latest international rare earth prices as an example, as shown in Table 2 below.

[0137] Table 2. Comparison of common rare elements of air electrodes and the prices of non-precious metals used in the present invention (ten thousand yuan / ton)

[0138]

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

[0140] One ton of CaFe is prepared by the present invention 0.5 Al 0.25 Cu 0.25 O 3-δ The material cost of the air electrode is 41,295 yuan, while the material cost of 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] As described above, it is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A preparation method of an air electrode with high catalytic activity, characterized in that, It includes the following steps: S1. Synthesize CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material, where 0 ≤ δ < 1; S2. Load the CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material on the acid-treated electrolyte to obtain a supported electrolyte, and sinter the supported electrolyte at 800°C to 1100°C; S3. Impregnate the supported electrolyte with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2, and then sinter at 800 °C to 1100 °C to obtain an air electrode with high catalytic activity.

2. The preparation method according to claim 1, wherein The CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material is synthesized by at least one of sol-gel method, solid-phase method, co-precipitation method and hydrothermal method.

3. The preparation method according to claim 2, wherein When synthesizing CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ materials by using the sol-gel method, the 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, and Cu(NO3)2 into water, heat and mix until dissolved to obtain a mixed solution; Add a first complexing agent, a second complexing agent and a pH regulator into the mixed solution to obtain a sol; Heat and mix the sol until the water evaporates and it becomes gel-like, then dry, fire, and pulverize 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, nitrilotriacetic acid, and diethylenetriaminepenta-carboxylate; The second complexing agent is selected from one or more of citric acid, malic acid, and oxalic acid; The pH regulator is selected from one or more of ammonia water, acetone, and ethanolamine; The mass ratio of the added 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 °C to 200 °C, and the time is 4 h to 6 h; The firing temperature is 900 °C to 1100 °C, and the time is 4 h to 6 h.

5. The preparation method according to claim 1, characterized in that In S2, The acid-treated electrolyte is the electrolyte treated with nitric acid with a mass fraction of 60% - 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; The sintering time is 1 h to 3 h.

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 impregnation time is 3 s to 10 s; The mass ratio of Fe(NO3)3 and Cu(NO3)2 is 1 - 2:1 - 2; The sintering time is 4 h to 6 h.

7. A high catalytic activity air electrode, characterized in that, Obtained by using the preparation method according to any one of claims 1 - 6.

8. A solid oxide fuel cell, characterized in that, Including the air electrode according to claim 7.

9. A method for preparing a solid oxide fuel cell as claimed in claim 8, characterized in that, The solid oxide fuel cell is a symmetric cell, and the preparation method of the solid oxide fuel cell includes the following steps: Add NiO into the electrolyte powder, press into a mold and calcine to obtain an electrolyte; Treat the electrolyte with acid to obtain an acid-treated electrolyte; Mix the synthesized CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material with isopropanol, ethylene glycol and glycerol, and ball-mill to obtain an air electrode paste; Load the air electrode slurry on the acid-treated electrolyte, sinter at 800 °C to 1100 °C, then impregnate with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2, and continue to sinter at 800 °C to 1100 °C to obtain a symmetric 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: Press the anode powder into a mold to obtain an anode, wherein the anode powder includes NiO, electrolyte and starch; The electrolyte is set on the anode surface, pressed, and calcined to obtain a half-cell; The electrolyte part of the half-cell is treated with an acid to obtain an acid-treated electrolyte; Mix the synthesized CaFe 0.5 Al 0.25 Cu 0.25 O 3-δ material with isopropanol, ethylene glycol and glycerol, and ball-mill to obtain an air electrode slurry; The air electrode paste is loaded on the acid-treated electrolyte, sintered at 800 °C to 1100 °C, then impregnated with a mixed salt solution containing Fe(NO3)3 and Cu(NO3)2, and further sintered at 800 °C to 1100 °C to obtain a single cell.

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