Composite cathode material of medium-temperature solid oxide fuel cell as well as preparation method and application of composite cathode material

Abstract

The invention discloses a composite cathode material of a medium-temperature solid oxide fuel cell as well as a preparation method and application of the composite cathode material, and relates to the technical field of fuel cells. The chemical general formula of the raw material composition of the composite cathode material is Pr < 0.4 > Sr < 0.6 > Co < 1-x > Ni < x > O < 3-delta >, and x is greater than or equal to 0.1 and less than or equal to 0.2. The two-phase (x = 0.1) or three-phase (x = 0.2) composite material obtained from (Pr0. 4Sr0. 6) 0.95 Co1-xNixO3-delta obviously improves the reaction kinetics of oxygen dissociation and oxygen migration in the oxygen reduction reaction, and provides a design thought for designing a cathode material with high catalytic activity.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a composite cathode material for a medium-temperature solid oxide fuel cell, a preparation method thereof, and applications thereof. Background Art

[0002] A lot of research has been done on the design and development of high catalytic activity SOFC composite cathode materials. 1-x Ca x Co2O 5+δ , 0.001≤x≤1.0. Calcium doping was used to control the content of simple cubic perovskite and double perovskite phases, optimizing the oxygen ion transport pathway and behavior during the oxygen reduction reaction.

[0003] Prior art also discloses a nanocathode material composed of nano-oxide and oxygen ion conductive material powders. The nano-oxide can be one of spinel oxides, perovskite oxides, double perovskite oxides, or a mixture of the two. First, the nano-oxide and oxygen ion conductive material powders are prepared, mixed and ground in varying proportions to form an electrode slurry. This is then applied to the electrolyte layer and calcined to produce a micron-sized cathode. The micron-sized cathode is then removed, and the electrode slurry is reapplied. After calcination, the solid oxide fuel cell nanocomposite cathode is obtained.

[0004] The overexploitation and inefficient use of fossil energy, and the resulting environmental problems, have become critical factors in social and economic development. Solid oxide fuel cells (SOFCs) are energy conversion devices that directly convert the chemical energy of fuels into electrical energy. They offer advantages such as high energy conversion efficiency, strong fuel adaptability, and environmental friendliness. However, excessively high operating temperatures accelerate the aging of cell components, hindering the commercialization of SOFCs. Lowering operating temperatures is crucial for practical applications. Unfortunately, lower operating temperatures slow the oxygen surface exchange processes (adsorption, dissociation, and reduction), ultimately leading to a decrease in catalytic performance for the oxygen reduction reaction (ORR). Therefore, the key to obtaining excellent cathode catalysts is to improve the cathode's catalytic performance at low temperatures. To address the above-mentioned shortcomings of the prior art, the present invention proposes a cathode material for medium- and low-temperature solid oxide fuel cells with a composite phase structure, which exhibits high oxygen reduction activity in the medium- and low-temperature range. Summary of the Invention

[0005] To address the shortcomings of the aforementioned background technology, the present invention primarily addresses the problem that excessively high operating temperatures in existing fuel cells accelerate the aging of cell components, hindering the commercialization of SOFCs. Conversely, lower operating temperatures slow the oxygen surface exchange process (adsorption, dissociation, and reduction), ultimately leading to a decrease in catalytic performance for the oxygen reduction reaction (ORR).

[0006] The present invention provides a composite cathode material for a medium-temperature solid oxide fuel cell, a preparation method thereof, and an application thereof. The composite cathode material can be used to obtain a perovskite phase (Pr / Sr)(Co / Ni)O by a one-pot process. 3-δ Ni with rock salt 2 / 3 Co 1 / 3 O can regulate the oxygen ion transport path and behavior in the material, thereby improving the oxygen catalytic reduction performance of the material as a medium- and low-temperature SOFC cathode material. (Pr / Sr)(Co / Ni)O with a composite phase structure 3-δ &Ni 2 / 3 Co 1 / 3 The polarization resistance of the O sample at 650 ℃ is only 0.137Ω / cm 2 , only the original sample Pr 0.4 Sr 0.6 CoO 3-δ The cathode material exhibits high electrical conductivity, exceeding 100 S / cm in the temperature range of 300-800°C, fully meeting the cathode conductivity requirement of 100 S / cm for solid oxide fuel cells. The composite cathode material has controllable composition, a simple and feasible synthesis method, and excellent catalytic activity for the oxygen reduction reaction.

[0007] The first object of the present invention is to provide a composite cathode material for a medium-temperature solid oxide fuel cell, wherein the raw material composition of the composite cathode material has the general chemical formula: (Pr 0.4 Sr 0.6 ) 0.95 Co 1-x Ni x O 3-δ , where 0.1≤x≤0.2.

[0008] Preferably, the raw material composition chemical formula of the composite cathode material includes: (Pr 0.4 Sr 0.6 ) 0.95 Co 0.9 Ni 0.1 O 3-δ 、(Pr 0.4 Sr 0.6 ) 0.95 Co 0.8 Ni 0.2 O 3-δ .

[0009] A second object of the present invention is to provide a method for preparing a composite cathode material for a medium-temperature solid oxide fuel cell, comprising the following steps: According to the chemical formula of raw materials (Pr 0.4 Sr 0.6 ) 0.95 Co 1-x Ni x O 3-δ Weigh the raw materials according to the molar ratio of each element in the mixture, and evenly disperse the raw materials in the water solvent to obtain a mixed solution; adding a complexing agent to the mixed solution to complex the metal ions in the mixed solution to obtain a gel solution; The gel solution is naturally expanded to obtain a precursor; The precursor is ground into powder and calcined to obtain a composite cathode material for a medium-temperature solid oxide fuel cell.

[0010] Preferably, the complexing agent comprises ethylenediaminetetraacetic acid and citric acid; The molar ratio of the ethylenediaminetetraacetic acid, citric acid and the total amount of metal elements in the raw materials is 1:2:1.

[0011] Preferably, the gel solution is prepared according to the following steps: The complexing agent is added to the mixed solution in multiple times, and the pH of the solution is adjusted to 7-8 with ammonia water to fully dissolve the EDTA. The solution is then placed in a water bath at 75-85°C and stirred to complex the metal ions in the mixed solution to obtain a gel solution.

[0012] Preferably, the natural expansion process is to keep the gel solution at 200-300°C for 2-4 hours.

[0013] Preferably, the calcination temperature is 950-1100° C., and the holding time is 3-6 h.

[0014] The third object of the present invention is to provide an application of a composite cathode material for a medium-temperature solid oxide fuel cell in a fuel cell.

[0015] A fourth object of the present invention is to provide a fuel cell comprising a composite cathode material for a medium-temperature solid oxide fuel cell.

[0016] A fifth object of the present invention is to provide a method for preparing a fuel cell, comprising the following steps: Grind the composite cathode material into 0.3-0.8 μm powder; Add powder, binder, pore-forming agent to an appropriate amount of terpineol and mix well to obtain cathode slurry; The cathode slurry is evenly coated on a dense electrolyte substrate and calcined at 950-1100°C for 1-3 hours to obtain a fuel cell. Among them, the electrolyte substrate is La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 2.8 Electrolyte base; binder is ethyl cellulose; pore-forming agent is soluble starch.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a composite cathode material for a medium-temperature solid oxide fuel cell, a preparation method thereof, and an application thereof. The present invention achieves the effect of (Pr 0.4 Sr 0.6 ) 0.95 Co 1-x Ni x O 3-δ Simple perovskite phase (Pr / Sr)(Co / Ni)O 3-δ , Rp phase (Pr / Sr)2(Co / Ni)O 4-δ Different composite materials were obtained by adjusting the content of Ni2CoO3 in the rock salt phase. Specifically, when x=0.1, (Pr / Sr)(Co / Ni)O 3-δ &Ni2CoO3(PSCN 113 -NCO) dual-phase composite material. When x=0.2, (Pr / Sr)(Co / Ni)O 3-δ &(Pr / Sr)2(Co / Ni)O 4-δ &Ni2CoO3(PSCN 113-214 -NCO) three-phase composite material. The heterogeneous interface between the rock salt phase and the simple perovskite phase in the composite cathode material provided by the present invention promotes charge transfer; the Rp phase material provides interstitial oxygen for the ORR, accelerating oxygen dissociation and transfer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 PSCN 113 -XRD spectrum of NCO; Figure 2 SEM images of PSCN-NCO powder at different magnifications; Figure 3 PSCN 113 -Element distribution map of NCO; Figure 4 PSCN 113 -Distribution of Co and Ni in NCO (along Figure 2 in the direction of the orange dotted arrow); Figure 5 Schematic diagram of the structure of NCO and PSCN; Figure 6 PSCN 113 -NCO conductivity variation at 300-800 ℃; Figure 7 PSC and PSCN at 650 ℃ 113 -NCO impedance change diagram; Figure 8 PSCN 113-214 -XRD spectrum of NCO; Figure 9 PSC and PSCN at 650 ℃ 113-214 -NCO conductivity relaxation curve. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0020] The present invention aims to provide a composite cathode material for medium-temperature solid oxide fuel cells, as well as its preparation method and application. This addresses the problem in existing fuel cells where excessively high operating temperatures accelerate the aging of cell components, hindering the commercialization of SOFCs. Lower operating temperatures, on the other hand, slow the oxygen surface exchange process (adsorption, dissociation, and reduction), ultimately leading to a decrease in catalytic performance for the oxygen reduction reaction (ORR).

[0021] In order to achieve the above object, the first aspect of the present invention provides a composite cathode material for a medium-temperature solid oxide fuel cell, wherein the raw material composition of the composite cathode material has the general chemical formula: (Pr 0.4 Sr 0.6 ) 0.95 Co 1-x Ni x O 3-δ , where 0.1≤x≤0.2.

[0022] The composite cathode material provided by the present invention has high oxygen catalytic reduction activity in the medium and low temperature range.

[0023] Wherein, the raw material composition chemical formula of the composite cathode material includes: (Pr 0.4 Sr 0.6 ) 0.95 Co 0.9 Ni 0.1 O 3-δ 、(Pr 0.4 Sr 0.6 ) 0.95 Co0.8 Ni 0.2 O 3-δ .

[0024] A second aspect of the present invention provides a method for preparing a composite cathode material for a medium-temperature solid oxide fuel cell, comprising the following steps: According to the chemical formula of raw materials (Pr 0.4 Sr 0.6 ) 0.95 Co 1-x Ni x O 3-δ Weigh the raw materials according to the molar ratio of each element in the mixture, and evenly disperse the raw materials in the water solvent to obtain a mixed solution; adding a complexing agent to the mixed solution to complex the metal ions in the mixed solution to obtain a gel solution; The gel solution is naturally expanded to obtain a precursor; The precursor is ground into powder and calcined to obtain a composite cathode material for a medium-temperature solid oxide fuel cell.

[0025] The present invention is based on the chemical formula (Pr 0.4 Sr 0.6 ) 0.95 Co 1-x Ni x O 3-δ Weigh the raw materials and obtain the perovskite phase (Pr / Sr)(Co / Ni)O by a one-pot process. 3-δ Ni with rock salt 2 / 3 Co 1 / 3 O can be used to regulate the oxygen ion transport path and behavior in the material, thereby improving the oxygen catalytic reduction performance of the material as a medium- and low-temperature SOFC cathode material.

[0026] Wherein, the complexing agent includes ethylenediaminetetraacetic acid and citric acid; The molar ratio of the ethylenediaminetetraacetic acid, citric acid and the total amount of metal elements in the raw materials is 1:2:1.

[0027] The gel solution was prepared according to the following steps: The complexing agent is added to the mixed solution in multiple times, and the pH of the solution is adjusted to 7-8 with ammonia water to fully dissolve the EDTA. The solution is then placed in a water bath at 75-85°C and stirred to complex the metal ions in the mixed solution to obtain a gel solution.

[0028] The natural expansion process is to keep the gel solution at 200~300℃ for 2~4 hours.

[0029] The calcination temperature is 950-1100° C., and the holding time is 3-6 h.

[0030] (Pr / Sr)(Co / Ni)O with composite phase structure prepared by the present invention 3-δ &Ni 2 / 3 Co 1 / 3 The polarization resistance of the O sample at 650 ℃ is only 0.137 Ω / cm 2 , only the original sample Pr 0.4 Sr 0.6 CoO 3-δ The cathode material exhibits high electrical conductivity, exceeding 100 S / cm in the temperature range of 300-800°C, fully meeting the cathode conductivity requirement of 100 S / cm for solid oxide fuel cells. The composite cathode material has controllable composition, a simple and feasible synthesis method, and excellent catalytic activity for the oxygen reduction reaction.

[0031] The present invention synthesizes the A-vacancy perovskite material Pr 0.4 Sr 0.6 Co 1-x Ni x O 3-δ (PSCN) was constructed by in situ self-assembly method. 3-δ The composite material of Ni2CoO3 and rock salt phase is used in SOFC cathode materials, and the impedance is significantly reduced. For example, the specific synthesis method is: (1) According to the chemical formula of raw materials Pr 0.4 Sr 0.6 Co 1-x Ni x O 3-δ (δ represents the non-stoichiometric coefficient of oxygen) and the molar ratio of each element was calculated to calculate the amount of Pr(NO3)3•6H2O, Co(NO3)2•6H2O, Sr(NO3)2, and Ni(NO3)2·6H2O to be added, which was dissolved in an appropriate amount of deionized water and stirred slowly until the solution was clear.

[0032] (2) Citric acid and ethylenediaminetetraacetic acid (EDTA) are used as complexing agents. The molar ratio of EDTA to citric acid and the total amount of metal ions added is 1:2:1. Add small amounts to the solution several times. Since EDTA is insoluble in acidic conditions, adjust the pH of the solution to 7-8 with ammonia water to fully dissolve the EDTA and turn the solution into a purple-black clear solution. Place the beaker in a constant temperature water bath at 80 °C and maintain medium stirring to fully complex the metal ions. The water evaporates to obtain a viscous purple-black gel.

[0033] (4) Place the beaker in an oven, heat it to 250 °C and keep it warm for 3 h to allow the gel to spontaneously ignite and expand, obtaining a fluffy black precursor.

[0034] (5) The precursor was ground into powder in an agate mortar, placed in a crucible, and calcined in a high-temperature muffle furnace. The temperature was maintained at 1000 °C for 5 h using a programmed temperature method to remove organic matter and nitrate particles in the precursor to form a composite material.

[0035] A third aspect of the present invention provides an application of a composite cathode material of a medium-temperature solid oxide fuel cell in a fuel cell.

[0036] A fourth aspect of the present invention provides a fuel cell comprising a composite cathode material for a medium-temperature solid oxide fuel cell.

[0037] A fifth aspect of the present invention provides a method for preparing a fuel cell, comprising the following steps: Grind the composite cathode material into 0.3-0.8 μm powder; Add powder, binder, pore-forming agent to an appropriate amount of terpineol and mix well to obtain cathode slurry; The cathode slurry is evenly coated on a dense electrolyte substrate and calcined at 950-1100°C for 1-3 hours to obtain a fuel cell. Among them, the electrolyte substrate is La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 2.8 Electrolyte base; binder is ethyl cellulose; pore-forming agent is soluble starch.

[0038] Exemplarily, a method for preparing a fuel cell comprises the following steps: The cathode material prepared above was placed in a ball mill and milled at 350 r / min for 4 h using anhydrous ethanol as a dispersant to obtain cathode powder with a particle size of 0.3-0.8 μm. 0.1 g of electrode material powder was weighed, 8% (wt%) ethyl cellulose was used as a binder, 12% (wt%) soluble starch was used as a pore-forming agent, and 4-5 drops of terpineol (about 0.2-0.25 ml) were added and mixed in a mortar to prepare a cathode slurry. The slurry was evenly coated on a dense La substrate using a 200 mesh screen using a screen printing method. 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 2.8 (LSGM) electrolyte substrate and calcined at 1000 °C for 2 h to obtain a symmetrical battery with the composite material as electrode and LSGM as electrolyte.

[0039] The LSGM electrolyte substrate is prepared according to the following steps: First, 10 g of LSGM was added to a 5% polyvinyl alcohol (PVA) solution as a binder in a 2:1 ratio of LSGM to PVA. The two were thoroughly mixed by grinding until the mixture became a dry, fine powder. 0.3–0.35 g of the powder was then weighed and poured into a tablet press. The press was maintained at a pressure of 10 MPa for 10 minutes, followed by a pressure of 20 MPa for 10 minutes, to form a compact green sheet with a diameter of 15 mm. The sheet was then spread onto a setter plate and calcined at a programmed temperature of 1450°C for 8 hours to produce a dense, black electrolyte.

[0040] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0041] Example 1 According to 0.01 mol Pr 0.4 Sr 0.6 Co 0.9 Ni 0.1 O 3-δ 1.74 g Pr(NO3)3·6H2O (analytical grade), 1.27 g Sr(NO3)2 (analytical grade), 2.62 g Co(NO3)2·6H2O (analytical grade), 0.29 g Ni(NO3)2·6H2O (analytical grade), and 8.41 g anhydrous citric acid were weighed, 500 ml deionized water was added, and the mixture was stirred until the solution was clear. 5.84 g ethylenediaminetetraacetic acid was added, and the pH of the solution was adjusted to 7-8 with ammonia water. The mixture was stirred in a constant temperature water bath at 80 °C until the water evaporated and the solution became a reddish-brown transparent gel. The gel was then placed in an oven at 250 °C for 3 h to obtain a black-gray fluffy precursor. After grinding into powder, the precursor was calcined in a muffle furnace at 1000 °C for 5 h to obtain (Pr / Sr)(Co / Ni)O 3-δ &Ni 2 / 3 Co 1 / 3 O composite materials (PSCN 113 -NCO), XRD analysis showed that the prepared oxide was a dual-phase composite material (such as Figure 1 ).

[0042] See also Figure 2 As shown, the microscopic morphology of the prepared powder was observed, PSCN 113 -NCO powder SEM images show that the powder particles are irregular in shape, see Figure 2The center-right image, a close-up at high magnification, clearly shows smaller nanoparticles attached to the surface of larger particles. These evenly distributed particles likely originate from the rock salt nanostructure formed during the in situ self-assembly process. The interface between the larger and smaller particles is clear, with no apparent agglomeration.

[0043] See also Figure 3 As shown in Figure 2, the microstructural characteristics of the material were analyzed by transmission electron microscopy. Figure 3 PSCN 113 High-resolution transmission image and analysis results of -NCO. The distribution of Ni, Co, and O within the area marked by the blue dashed line indicates that the metal cations in the rock salt phase are primarily composed of Co and Ni. The remaining area shows a uniform distribution of Pr, Sr, Co, Ni, and O, while Ni is relatively low in content, indicating that it primarily forms the rock salt phase on the material surface.

[0044] To further verify the element distribution characteristics of the interface area, quantitative analysis was performed on the selected area. Figure 4 Showing along Figure 3 The line scan curve of the pink dotted arrow shows that when the scanning track passes through the NCO region, the Ni content increases significantly, while the Pr and Sr content decreases to the baseline level. The Ni / Co atomic ratio in the NCO region is close to 2:1, and the corresponding chemical composition is Ni 2 / 3 Co 1 / 3 O. At the same time, the doping amount of Ni element in the B site of PSCN phase is low, and its chemical composition can be expressed as Pr 0.4 Sr 0.6 Co 0.95 Ni 0.05 O 3-δ Based on the above characterization results, the phase composition and element distribution characteristics of the heterostructure can be clearly determined. Figure 5 As shown, the rock salt phase Ni 2 / 3 Co 1 / 3 Ni and Co atoms in O occupy octahedral sites in a disordered manner, and their crystal structure is isomorphic to that of NiO and CoO. This rock salt phase and the PSCN perovskite phase self-assemble in situ to form a heterojunction composite material. This structure is expected to optimize the physicochemical properties at the interface, providing a good foundation for improving electrochemical performance.

[0045] Put (Pr / Sr)(Co / Ni)O 3-δ &Ni 2 / 3 Co 1 / 3 O composite materials (PSCN 113-NCO) powder was placed in a tablet press mold and pressed into a 5×5×20 mm strip at a pressure of 200 MPa. The sample was sintered at 1150 °C in an air atmosphere for 3 h using a programmed temperature sintering method to obtain a denser sample. Four parallel silver wires were bonded to the strip sample with silver paste as silver wires for voltage and current respectively. The conductivity of the sample in an air atmosphere was tested using a four-probe test method. Direct current was passed through both ends of the sample. The voltage between the two voltage lines was measured with a digital multimeter to obtain the sample resistance value between the two voltage lines. The conductivity of the sample can then be calculated using the formula σ = L / SR (σ is the sample conductivity, in S / cm, L is the distance between the two voltage lines, S is the cross-sectional area of ​​the sample strip, and R is the resistance between the two voltage lines measured by the multimeter). The test temperature range is 250-800 °C, and the data is tested every 50 °C. Figure 6 As shown, as the temperature increases, PSFC 113 The conductivity of -NCO increases first and then decreases. Within the operating temperature range, the conductivity value is much greater than 100 S / cm, which meets the cathode requirements.

[0046] Example 2 Weigh the PSCN prepared in Example 1 113 -NCO as cathode material 0.1 g, 8 mg ethyl cellulose, 12 mg soluble starch, terpineol as solvent, grind and mix to prepare cathode slurry. 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ (LSGM) was used as the electrolyte, and the cathode slurry was coated on both sides of the electrolyte by screen printing to prepare a symmetrical battery. Silver wire was used as the current collector, and the impedance of the symmetrical battery was tested at 650 °C in air. Figure 7 PSCN available 113 The polarization resistance of the -NCO material at 650 °C is approximately 0.137 Ω cm 2 Under the same conditions, Pr 0.4 Sr 0.6 CoO 3-δ The polarization resistance value of the (PSC) material (0.61 Ω cm 2 ) is much larger than this value. 113 -NCO composites exhibit excellent oxygen reduction catalytic activity as low-temperature SOFC cathode materials.

[0047] Example 3 According to 0.01 mol Pr 0.4 Sr 0.6 Co 0.8 Ni0.3 O 3-δ 1.74 g Pr(NO3)3·6H2O (analytical grade), 1.27 g Sr(NO3)2 (analytical grade), 2.33 g Co(NO3)2·6H2O (analytical grade), 0.87 g Ni(NO3)2·6H2O (analytical grade), and 8.41 g citric acid monohydrate were weighed, added to 500 ml deionized water, and stirred until the solution was clear. 5.84 g ethylenediaminetetraacetic acid was added, and the pH of the solution was adjusted to 7-8 with ammonia water. The solution was stirred in a constant temperature water bath at 80 °C until the water evaporated and the solution became a reddish-brown transparent gel. The gel was then placed in an oven at 250 °C for 3 h to obtain a black-gray fluffy precursor. After grinding into powder, it was calcined in a muffle furnace at 1000 °C for 5 h to obtain (Pr / Sr)(Co / Ni)O 3-δ &(Pr / Sr)2(Co / Ni)O 4-δ &Ni 2 / 3 Co 1 / 3 O3 composite material (PSCN 113 - 214 &NCO), XRD analysis showed that the prepared oxide was a three-phase composite material (such as Figure 8 ).

[0048] PSCN 113 - 214 The NCO composite material powder was placed in a tablet press mold and pressed into a 5×5×20 mm strip at a pressure of 200 MPa. The sample was sintered at 1150°C in air for 3 h using a programmed temperature sintering method to obtain a relatively dense test sample. Four parallel silver wires were bonded to the strip sample with silver paste as silver wires for voltage and current, respectively. The sample was placed in a tubular furnace, and a gas mass flowmeter was used to introduce a mixture of nitrogen and oxygen into the furnace in proportion to cause a sharp change in the oxygen partial pressure. The oxygen partial pressure was controlled to switch between 0.21 atm and 0.1 atm, and the gas flow rate was 100 mL / min. -1 The sample is placed in a closed quartz tube and the change in instantaneous conductivity is recorded. Figure 9 As shown in Figure 2, at 650 °C, the time it takes for the three-phase composite material to reach re-equilibrium is only 1700 seconds, while the Pr 0.4 Sr 0.6 CoO 3-δ The material takes nearly 2500 seconds to re-equilibrate. The heterojunction between the rock salt layer and the perovskite in the three-phase material accelerates electron transport, while the interstitial oxygen in the RP phase accelerates the migration of oxygen species. Consequently, the time it takes for the material to reach re-equilibrium is significantly shortened.

[0049] For this reason, in the present invention, (Pr 0.4 Sr 0.6 )0.95 Co 1-x Ni x O 3-δ The obtained two-phase (x=0.1) or three-phase (x=0.2) composite materials significantly improved the reaction kinetics of oxygen dissociation and oxygen migration in the oxygen reduction reaction, providing design ideas for the design of cathode materials with high catalytic activity.

[0050] In summary, the present invention provides a medium- and low-temperature solid oxide fuel cell cathode material with a composite phase structure, and its general composition formula is: Pr 0.4 Sr 0.6 Co 1-x Ni x O 3-δ ,0.1≤x≤0.2. The fuel cell cathode material of the present invention can obtain the perovskite phase (Pr / Sr)(Co / Ni)O by a one-pot process. 3-δ Ni with rock salt 2 / 3 Co 1 / 3 O can regulate the oxygen ion transport path and behavior in the material, thereby improving the oxygen catalytic reduction performance of the material as a medium- and low-temperature SOFC cathode material. (Pr / Sr)(Co / Ni)O with a composite phase structure 3-δ &Ni 2 / 3 Co 1 / 3 The polarization resistance of the O sample at 650 ℃ is only 0.137 Ω / cm 2 , only the original sample Pr 0.4 Sr 0.6 CoO 3-δ The cathode material exhibits high electrical conductivity, exceeding 100 S / cm in the 300-800°C range, fully meeting the 100 S / cm cathode conductivity requirement for solid oxide fuel cells. The composite cathode material has controllable composition, a simple and feasible synthesis method, and excellent catalytic activity for the oxygen reduction reaction.

[0051] The present invention describes preferred embodiments and their effects. However, those skilled in the art, once informed of the basic inventive concept, may make additional changes and modifications to these embodiments. Therefore, it is intended that the appended claims be interpreted to include the preferred embodiments as well as all changes and modifications that fall within the scope of the invention.

[0052] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A composite cathode material for a medium-temperature solid oxide fuel cell, characterized in that: The chemical formula of the raw material composition of the composite cathode material is: (Pr 0.4 Sr 0.6 ) 0.95 Co 1-x Ni x O 3-δ , where 0.1≤x≤0.

2.

2. The composite cathode material for a medium-temperature solid oxide fuel cell according to claim 1, characterized in that: The raw material composition chemical formula of the composite cathode material includes: (Pr 0.4 Sr 0.6 ) 0.95 Co 0.9 Ni 0.1 O 3-δ 、(Pr 0.4 Sr 0.6 ) 0.95 Co 0.8 Ni 0.2 O 3-δ .

3. A method for preparing a composite cathode material for a medium-temperature solid oxide fuel cell according to claim 1 or 2, characterized in that: The following steps are involved: According to the chemical formula of raw materials (Pr 0.4 Sr 0.6 ) 0.95 Co 1-x Ni x O 3-δ Weigh the raw materials according to the molar ratio of each element in the mixture, and evenly disperse the raw materials in the water solvent to obtain a mixed solution; adding a complexing agent to the mixed solution to complex the metal ions in the mixed solution to obtain a gel solution; The gel solution is naturally expanded to obtain a precursor; The precursor is ground into powder and calcined to obtain a composite cathode material for a medium-temperature solid oxide fuel cell.

4. The method for preparing a composite cathode material for a medium-temperature solid oxide fuel cell according to claim 3, wherein: The complexing agent includes ethylenediaminetetraacetic acid and citric acid; The molar ratio of the ethylenediaminetetraacetic acid, citric acid and the total amount of metal elements in the raw materials is 1:2:

1.

5. The method for preparing a composite cathode material for a medium-temperature solid oxide fuel cell according to claim 4, wherein: The gel solution was prepared according to the following steps: The complexing agent is added to the mixed solution in multiple times, and the pH of the solution is adjusted to 7-8 with ammonia water to fully dissolve the EDTA. The solution is then placed in a water bath at 75-85°C and stirred to complex the metal ions in the mixed solution to obtain a gel solution.

6. The method for preparing a composite cathode material for a medium-temperature solid oxide fuel cell according to claim 3, wherein: The natural expansion process is to keep the gel solution at 200~300℃ for 2~4 hours.

7. The method for preparing a composite cathode material for a medium-temperature solid oxide fuel cell according to claim 3, wherein: The calcination temperature is 950-1100°C, and the holding time is 3-6 hours.

8. Use of the composite cathode material for a medium-temperature solid oxide fuel cell according to claim 1 or 2 in a fuel cell.

9. A fuel cell, characterized in that: A composite cathode material for a medium-temperature solid oxide fuel cell comprising the material of claim 1 or 2.

10. A method for preparing a fuel cell according to claim 9, characterized in that: The following steps are involved: Grind the composite cathode material into 0.3-0.8 μm powder; Add powder, binder, pore-forming agent to an appropriate amount of terpineol and mix well to obtain cathode slurry; The cathode slurry is evenly coated on a dense electrolyte substrate and calcined at 950-1100°C for 1-3 hours to obtain a fuel cell. Among them, the electrolyte substrate is La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 2.8 Electrolyte base; binder is ethyl cellulose; pore-forming agent is soluble starch.

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