CN104752734A - Low-temperature solid oxide fuel cell cathode in core-shell nano fiber structure and electrostatic spinning preparation method thereof - Google Patents

Abstract

A low-temperature solid oxide fuel cell cathode in a core-shell nanofiber structure and an electrospinning preparation method thereof belong to the field of functional materials. The core-shell nanofiber structure cathode is composed of a nanofiber core and a nanoshell layer, and the fiber core and shell layer are respectively composed of a perovskite structure ion-electronic mixed conductor component A and an oxygen ion conductor electrolyte component B, or a combination of The above-mentioned core-shell nanofiber cathode is prepared by electrospinning, and component A and component B spinning precursor solutions are prepared respectively, and the two solutions are respectively injected into the inner layer or the outer layer spinning channel for spinning, The composite fiber is dried and sintered at high temperature to obtain a core-shell nanofibrous structure cathode material. The core-shell nanofiber structure enhances the oxygen reduction catalytic activity of the medium-low temperature SOFC cathode, the ability to resist _CO2 surface adsorption poisoning, and the stability of structure and performance, and the process is simple and the cost is low.

Description

a nucleus - Low-temperature solid oxide fuel cell cathode in shell nanofiber structure and preparation method thereof by electrospinning

technical field

The invention relates to a low-temperature solid oxide fuel cell cathode in a core-shell nanofiber structure and an electrospinning preparation method thereof, belonging to the field of functional materials.

Background technique

Solid Oxide Fuel Cell (SOFC) is a green alternative energy source with great application prospects. It is an important development direction in the SOFC field to reduce the working temperature from high temperature of 1000 ℃ to medium and low temperature range of 500-700 ℃. As the operating temperature of SOFC decreases, the oxygen reduction catalytic activity of the cathode decreases, and the polarization impedance increases rapidly, which becomes the key factor limiting the output power of SOFC at medium and low temperature; the decrease of operating temperature will also intensify the adsorption and poisoning of _CO on the surface of the cathode, resulting The catalytic activity of the cathode further decreases, and the internal loss of the SOFC increases; in addition, the matching of the thermal expansion coefficient between the cathode and the electrolyte material also affects the structure and performance stability of the SOFC during preparation and thermal cycling. Therefore, the development of cathode materials with high oxygen reduction catalytic activity in the temperature range of 500-700 °C, resistance to _CO2 surface adsorption poisoning, and thermal expansion coefficient matching with electrolyte materials is of great significance to promote the development and application of medium and low temperature SOFCs.

Chen et al. (Yan Chen, Zhuhua Cai, Yener Kuru, Wen Ma, Harry L.Tuller, Bilge Yildiz, Advanced Energy Materials, 2013, 3, 1221.) prepared La _0.8 Sr _0.2 CoO ₃ / (La _0.5 Sr _0.5 ) ₂ CoO ₄ multilayer film with heterogeneous interface structure, the oxygen reduction reaction rate increases by several orders of magnitude at 500 °C, and the oxygen reduction catalytic activity of the cathode is significantly enhanced, but this multilayer film material requires expensive, special The cost of preparation equipment is high, which is not conducive to the mass production and large-scale application of the cathode, and cannot solve the problems of _CO2 surface adsorption poisoning and high thermal expansion coefficient of the cathode. Zhou et al. (Wei Zhou, Fengli Liang, Zongping Shao, Zhonghua Zhu, Scientific Reports, 2012, 2 : 327) used solution infiltration-microwave plasma heating method in Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _{3- δ} (BSCF) The La ₂ NiO _{4+ δ} protective layer prepared on the surface of the particles improves the catalytic activity and performance stability of the oxygen reduction reaction of the BSCF cathode in an atmosphere containing CO _{2 .} provides an effective solution, however, due to the low oxygen ion conductivity of the La ₂ NiO _{4+ δ} protective layer, which is not conducive to the oxygen surface exchange process of the cathode, the oxygen reduction catalytic activity of the prepared cathode is not high, and thermal expansion still exists The coefficient is too high.

Contents of the invention

In order to overcome the problems existing in the prior art, the present invention provides a low-temperature solid-state oxide fuel cell cathode in a core-shell nanofiber structure and its electrospinning preparation method, which enhances the low-temperature solid-state oxidation by constructing a core-shell nanofiber structure Oxygen reduction catalytic activity, anti-CO ₂ surface adsorption poisoning ability, and structure and performance stability of the cathode of the fuel cell, and it is prepared by electrospinning, which simplifies the preparation process and reduces the preparation cost.

The technical solution adopted in the present invention is: a low-temperature solid oxide fuel cell cathode in a core-shell nanofiber structure, the cathode in the core-shell nanofiber structure is composed of a nanofiber core and a nano-shell layer, and the nanofiber core and The nano shell layer is composed of the perovskite structure ion-electron mixed conductor oxide component A and the oxygen ion conductor electrolyte component B, or on the contrary, the nano shell is composed of the perovskite structure ion-electronic mixed conductor oxide component A Layer, the oxygen ion conductor electrolyte component B forms a nanofiber core; in the nanofiber structure, the diameter of the nanofiber core is 50-500 nanometers, and the thickness of the nano-shell layer is 100-800 nanometers.

An electrospinning preparation method for the cathode of a low-temperature solid oxide fuel cell in a core-shell nanofiber structure. First, the spinning precursor solution and the oxygen ion conductor electrolyte of the perovskite structure ion-electronic mixed conductor oxide component A are respectively prepared Component B spinning precursor solution, and then inject the two spinning precursor solutions into the inner and outer spinning channels respectively, or inject the perovskite structure ion-electronic mixed conductor oxide component A spinning precursor The solution and the oxygen ion conductor electrolyte component B spinning precursor solution are injected into the opposite spinning channel for coaxial spinning to prepare concentric composite fibers. The fibers are dried and sintered at high temperature to obtain the oxidized Two different core-shell nanofiber structure cathode materials composed of material component A and oxygen ion conductor electrolyte component B; the specific preparation steps of the core-shell nanofiber structure cathode of the present invention are as follows:

Step 1. Prepare the spinning precursor solution of the perovskite structure ion-electronic mixed conductor oxide component A spinning precursor solution and the oxygen ion conductor electrolyte component B spinning precursor solution respectively;

Perovskite structure ion-electronic mixed conductor oxide component A spinning precursor solution preparation process:

According to the stoichiometric ratio of the perovskite structure oxide, weigh the required acetate or nitrate reagent containing the corresponding metal ion, and dissolve it in deionized water-alcohol-N,N-dimethylformamide under magnetic stirring Mixed solvent, then dissolve polyvinylpyrrolidone in the above mixed solution under magnetic stirring; or, first dissolve polyvinylpyrrolidone in deionized water-alcohol-N,N-dimethylformamide mixed solvent under magnetic stirring , and then add the required acetate or nitrate reagent containing the corresponding metal ion, and magnetically stir until completely dissolved; the volume ratio of deionized water, alcohol and N,N-dimethylformamide solvent in the mixed solution is 0.1-0.5: 0.5-1 : 5-10, the amount of polyvinylpyrrolidone is 1.5-3 times the total mass of acetate and nitrate reagents in the above mixed solution; the uniformly mixed perovskite structure oxide spinning precursor The body solution is ultrasonically debubbled, and placed at room temperature for 5-15 hours;

Oxygen ion conductor electrolyte component B spinning precursor solution preparation process:

According to the stoichiometric ratio of the electrolyte oxide, weigh the required acetate or nitrate reagent containing the corresponding metal ion, and dissolve it in the mixed solvent of deionized water-alcohol-N,N-dimethylformamide under magnetic stirring , and then dissolve polyvinylpyrrolidone in the above mixed solution; or, first dissolve polyvinylpyrrolidone in a mixed solvent of deionized water-alcohol-N,N-dimethylformamide, and then add the required metal-containing Add ionic acetate or nitrate reagent, magnetically stir until completely dissolved; the volume ratio of deionized water, alcohol and N,N-dimethylformamide solvent in the mixed solution is 0.1-0.5: 0.5-1 : 5- 10. The amount of polyvinylpyrrolidone used is 1.5-3 times the total mass of acetate and nitrate reagents in the above mixed solution; to obtain the oxygen ion conductor electrolyte spinning precursor solution, the solution 2 is ultrasonically debubbled, and placed at room temperature for 5 -15 hours;

Step 2. Electrospinning preparation of core-shell nanofibers

Inject the perovskite structure ion-electronic mixed conductor oxide component A spinning precursor solution prepared above and the oxygen ion conductor electrolyte component B spinning precursor solution into the inner and outer channels of the electrospinning head respectively Inside, coaxial jetting, spinning conditions: flow rate of spinning solution 5-30 μl/min, spinning voltage 10-25kV, distance between spinning needle and receiver 5-15cm; the core-shell structure of nanofibers is composed of The perovskite structure ion-electron mixed conductor oxide component A spinning precursor solution and the oxygen ion conductor electrolyte component B spinning precursor solution are determined by the injection positions of the inner and outer channels, by changing the spinning voltage and The flow rate of the two spinning liquids is adjusted to the diameter of the fiber core and the thickness of the shell layer in the nanofibers to obtain core-shell concentric composite fibers with different structures, and then the fibers are dried in a drying oven at 40-80°C for 10-20 Hour;

Step 3. Core-shell nanofiber cathode sintering phase formation

The above dried concentric composite fibers are sintered at high temperature. The sintering conditions are: heating to 400-600°C at a heating rate of 3-6°C/min, keeping the temperature for 2-5 hours, and then heating at a rate of 5-10°C/min to 1000- 1150°C and keep it warm for 1-5 hours, and finally cool down to room temperature at a rate of 5-12°C/min. During this high-temperature sintering process, the perovskite structure oxide component and the oxygen ion conductor electrolyte component form phases respectively to form nuclei -Shell nanofiber cathode material.

For the convenience of further introducing the above-mentioned technical solution, component A of the perovskite structure ion-electronic mixed conductor oxide is referred to as component A for short, and component B of the oxygen ion conductor electrolyte is referred to as component B for short.

The beneficial effects of the present invention are:

1. The low-temperature solid oxide fuel cell cathode in the core-shell nanofiber structure is composed of a nanofiber core and a nano-shell layer, and the fiber core and the shell layer are respectively component A and component B, or the components are opposite; component A Provide the required electrons and oxygen ions for the cathode oxygen reduction reaction. Component B is an oxygen ion conductor material. The addition of component B can improve the oxygen ion conductivity, oxygen surface exchange and transmission rate of the cathode, and enhance the oxygen reduction catalysis of the cathode. Activity; Component B can also reduce the thermal expansion coefficient of the cathode, and as a protective layer will also improve the ability of the cathode to resist CO ₂ surface adsorption and poisoning, thereby improving the structure and performance stability of SOFC; and the nanofiber structure can increase the activation of the electrode reaction Area, promote oxygen surface exchange and bulk diffusion rate, further enhance the oxygen reduction catalytic activity of the cathode, and optimize the comprehensive performance of the cathode material of the medium and low temperature solid oxide fuel cell.

2. The provided method performs electrospinning and synchronous sintering of two spinning precursor solutions with different components to form a phase, and obtains a low-temperature solid oxide fuel cell cathode in a nanofiber structure composed of a nanofiber core and a nanoshell layer, and the nanofiber core The structure of the nano shell layer is determined by the injection position of the two spinning precursor solutions. The diameter of the fiber core and the thickness of the shell layer are conveniently regulated by changing the spinning voltage and the flow rate of the two spinning solutions. The preparation process is simple and the cost is low. lower.

Description of drawings

Figure 1 is a schematic diagram of electrospinning. The spinning precursor solution of component A and the spinning precursor solution of component B are respectively injected into the channels of the inner layer and the outer layer.

Fig. 2 is a schematic diagram of the side and cross-sectional structure of the core-shell nanofiber prepared by the electrospinning equipment shown in Fig. 1 . Component A acts as the fiber core, and Component B acts as the outer shell.

Figure 3 is another schematic diagram of electrospinning. The spinning precursor solution of component A and the spinning precursor solution of component B are respectively injected into the channels of the outer layer and the inner layer.

Fig. 4 is a schematic diagram of the side and cross-sectional structure of the core-shell nanofiber prepared by the electrospinning equipment shown in Fig. 3 . Component A is used as the shell layer, and component B is used as the fiber core.

Detailed ways

Further description will be made below through specific examples.

Low-temperature SOFC cathode material with core-shell nanofiber structure composed of perovskite oxide PrBa _0.92 Co ₂ O _{6- δ} (δ is oxygen deficiency) and electrolyte Gd _0.1 Ce _0.9 O _1.95 prepared by electrospinning

Step 1. Prepare PrBa _0.92 Co ₂ O _{6- δ} spinning precursor solution and Gd _0.1 Ce _0.9 O _1.95 spinning precursor solution respectively

Preparation process of PrBa _0.92 Co ₂ O _{6- δ} spinning precursor solution:

Accurately weigh Pr(NO ₃ ) _{3 ▪} 6H ₂ O _0.174g , Ba(NO ₃ ) ₂ 0.0961g, Co(Ac _{) 2 ▪} 4H ₂ according to the metal ion stoichiometric ratio of _0.4mmol PrBa 0.92 _Co 2 O 6-δ O 0.199g, put into a mixed solvent composed of 0.2ml deionized water, 0.5ml alcohol and 6ml N,N-dimethylformamide, magnetically stir at room temperature until the above reagents are completely dissolved and mixed uniformly; then 1.0 One gram of polyvinylpyrrolidone was dissolved in the above mixed solution under magnetic stirring to obtain a uniformly mixed PrBa _0.92 Co ₂ O _{6- δ} spinning precursor solution, the solution was ultrasonically debubbled, and placed at room temperature for 10 hours;

Preparation process of electrolyte Gd _0.1 Ce _0.9 O _1.95 spinning precursor solution:

Dissolve 0.35 g of polyvinylpyrrolidone in a mixed solvent consisting of 0.2 ml of deionized water, 0.5 ml of alcohol, and 2 ml of N,N-dimethylformamide, and magnetically stir at room temperature until completely dissolved; follow the synthesis method of 0.4 mmol Gd _0.1 Metal ion metering ratio of Ce _0.9 O _1.95 Weigh 0.156 g of Ce(NO ₃ ) _{3 ▪} 6H ₂ O, 0.018 g of Gd(NO ₃ ) _{3 ▪} 6H ₂ O, add to the above mixed solution, stir magnetically at room temperature until completely dissolved , to obtain the electrolyte Gd _0.1 Ce _0.9 O _1.95 spinning precursor solution, the solution 2 was ultrasonically debubbled, and left at room temperature for 10 hours.

Step 2. Electrospinning of PrBa _0.92 Co ₂ O _{6- δ} -Gd _0.1 Ce _0.9 O _1.95 core-shell nanofibers

Inject the PrBa _0.92 Co ₂ O _{6- δ} spinning precursor solution and the Gd _0.1 Ce _0.9 O _1.95 spinning precursor solution prepared above into the inner and outer channels of the electrospinning syringe, and adjust the spinning needle and The distance between the receivers is 10 cm, and the high pressure is 10-15 kV for coaxial spraying, and the flow rate of the PrBa _0.92 Co ₂ O _{6- δ} solution and the Gd _0.1 Ce _0.9 O _1.95 solution is controlled to 5-20 μl/min by using a syringe pump. Shaft spinning to obtain nanofibers with PrBa _0.92 Co ₂ O _{6- δ} component as the fiber core and Gd _0.1 Ce _0.9 O _1.9 component as the shell layer; change the injection position of the two spinning precursor solutions, that is, Gd _0.1 Ce _0.9 O _1.95 solution was injected into the inner channel of the electrospinning syringe, and PrBa _0.92 Co ₂ O _{6- δ} solution was injected into the outer channel for electrospinning, and the Gd _0.1 Ce _0.9 O _1.9 component was obtained as fiber core, PrBa _0.92 Co _{The 2} O _{6- δ} component is the concentric composite fiber of the shell layer; the obtained PrBa _0.92 Co ₂ O _{6- δ} -Gd _0.1 Ce _0.9 O _1.95 concentric composite fiber was dried in a 60°C drying oven for 20 hours.

Step 3, PrBa _0.92 Co ₂ O _{6- δ} -Gd _0.1 Ce _0.9 O _1.95 concentric composite fiber cathode sintering phase

Sinter the above dried PrBa _0.92 Co ₂ O _{6- δ} -Gd _0.1 Ce _0.9 O _1.95 concentric composite fibers at high temperature, first heating to 600 °C at a heating rate of 3 °C/min, keeping it for 3 hours, and then heating at a rate of 5 °C/min Heated to 1050°C and held for 2 hours, and finally cooled down to room temperature at a rate of 10°C/min to obtain two different structures of PrBa _0.92 Co ₂ O _{6- δ} -Gd _0.1 Ce _0.9 O _1.95 core-shell nanofiber cathode materials, in which PrBa _0.92 Co ₂ O _{6- δ} is an orthorhombic layered perovskite structure, and Gd _0.1 Ce _0.9 O _1.95 is a face-centered cubic structure. The obtained PrBa _0.92 Co ₂ O _{6- δ} -Gd _0.1 Ce _0.9 O _1.95 core-shell nanofiber cathode has an enhanced oxygen reduction catalytic activity of 30-80% at a temperature of 500-700 °C, a 20-40% decrease in thermal expansion coefficient, and an anti-CO ₂ The surface adsorption and poisoning ability is increased by 40-70%, and the comprehensive performance of the cathode is improved.

Claims (2)

1. low temperature solid-state oxide fuel battery cathode in a core-shell structure copolymer nanofibrous structures, it is characterized in that, described core-shell structure copolymer nanofibrous structures negative electrode is made up of nanofiber core and nanometer outer shell, described nanofiber core and nanometer outer shell are made up of perovskite structure ion-electron mixing conductor oxide component A and oxygen ion conductor electrolyte components B respectively, or it is contrary, form nanometer outer shell by perovskite structure ion-electron mixing conductor oxide component A, oxygen ion conductor electrolyte components B forms nanofiber core; In described nanofibrous structures, nanofiber nuclear diameter is 50-500 nanometer, and nanometer outer shell thickness is 100-800 nanometer.

2. the electrostatic spinning preparation method of low temperature solid-state oxide fuel battery cathode in a kind of core-shell structure copolymer nanofibrous structures according to claim 1, it is characterized in that, first respectively perovskite structure ion-electron mixing conductor oxide component A spinning precursor solution and oxygen ion conductor electrolyte components B spinning precursor solution is prepared, then two kinds of spinning precursor solutions are injected in internal layer and outer slinning cabinet respectively, or perovskite structure ion-electron mixing conductor oxide component A spinning precursor solution and oxygen ion conductor electrolyte components B spinning precursor solution are injected contrary slinning cabinet, carry out coaxial spinning, prepare concentric composite fibre, fiber drying, high temperature sintering, obtain the two kinds of different core-shell structure copolymer nanofibrous structures cathode materials be made up of perovskite structure ion-electron mixing conductor oxide component A and oxygen ion conductor electrolyte components B, the concrete preparation process of core-shell structure copolymer nanofibrous structures negative electrode of the present invention is as follows:

Step one, respectively preparation perovskite structure ion-electron mixing conductor oxide component A spinning precursor solution and oxygen ion conductor electrolyte components B spinning precursor solution;

Perovskite structure ion-electron mixing conductor oxide component A spinning precursor solution process for preparation:

According to the stoichiometric proportion of perovskite structure oxide, take the required acetate containing respective metal ion or nitrate reagent, deionization ethanol-water-N is dissolved under magnetic agitation, in dinethylformamide mixed solvent, then under magnetic stirring polyvinylpyrrolidone is dissolved in above mixed solution; Or, polyvinylpyrrolidone is dissolved in deionization ethanol-water-DMF mixed solvent first under magnetic stirring, and then by the required acetate containing respective metal ion or nitrate reagent adds, magnetic agitation is to dissolving completely; In mixed solution, the volume ratio of deionized water, alcohol and DMF solvent is 0.1-0.5:0.5-1: 5-10, and the consumption of polyvinylpyrrolidone is 1.5-3 times of acetate and nitrate reagent gross mass in above mixed solution; By the ultrasonic bubble that degass of perovskite structure oxide spinning precursor solution mixed, at room temperature place 5-15 hour;

Oxygen ion conductor electrolyte components B spinning precursor solution process for preparation:

According to the stoichiometric proportion of electrolyte oxide, take the required acetate containing respective metal ion or nitrate reagent, be dissolved in deionization ethanol-water-N under magnetic agitation, in dinethylformamide mixed solvent, then polyvinylpyrrolidone is dissolved in above mixed solution; Or, first polyvinylpyrrolidone is dissolved in deionization ethanol-water-DMF mixed solvent, and then by the required acetate containing respective metal ion or nitrate reagent adds, magnetic agitation is to dissolving completely; In mixed solution, the volume ratio of deionized water, alcohol and DMF solvent is 0.1-0.5:0.5-1: 5-10, and the consumption of polyvinylpyrrolidone is 1.5-3 times of acetate and nitrate reagent gross mass in above mixed solution; Obtain oxygen ion conductor electrolyte spinning precursor solution, by ultrasonic for solution 2 bubble that degass, at room temperature place 5-15 hour;

The electrostatic spinning preparation of step 2, core-shell structure copolymer nanofiber

In the internal layer respectively the perovskite structure ion-electron mixing conductor oxide component A spinning precursor solution for preparing above and oxygen ion conductor electrolyte components B spinning precursor solution being injected electrostatic spinning head and outer layer channel, carry out coaxial injection, spinning condition: the flow velocity 5-30 μ l/min of spinning solution, spinning voltage 10-25kV, the spacing 5-15cm of spinning syringe needle and recipient; The core-shell structure copolymer structure of nanofiber is determined in the injection phase of internal layer and outer layer channel by perovskite structure ion-electron mixing conductor oxide component A spinning precursor solution and oxygen ion conductor electrolyte components B spinning precursor solution, regulated and controled by the thickness of flow velocity to diameter fibronuclear in nanofiber and outer shell changing spinning voltage and two kinds of spinning solutions, obtain the concentric composite fibre of heteroid core-shell structure copolymer, then by fiber at 40-80 DEG C of drying box inner drying process 10-20 hour;

Step 3, core-shell structure copolymer nanofiber negative electrode sinter phase into

Above dry rear composite fibre is with one heart carried out high temperature sintering, sintering condition is: be heated to 400-600 DEG C with 3-6 DEG C/min of heating rate, insulation 2-5 hour, then be heated to 1000-1150 DEG C with 5-10 DEG C/min of speed and be incubated 1-5 hour, finally be cooled to room temperature with 5-12 DEG C/min of speed, in this high-temperature sintering process, perovskite structure oxide component respectively has phase of one's own with oxygen ion conductor electrolyte components, forms core-shell structure copolymer nanofiber cathode material.