In-situ precipitation of nano-catalytic particles CaxCo4O9+δ materials and their applications

Abstract

The present invention discloses a Ca x Co4O 9+δ material with in-situ precipitated nano-catalytic particles and its applications; the Ca x Co4O 9+δ material with in-situ precipitated nano-catalytic particles is obtained by annealing Ca x Co4O 9+δ in air to achieve in-situ precipitation of Co3O4 and Ca(OH)2 catalytic nanoparticles on the surface of Ca3Co4O 9+δ , and it is applied to the cathode of solid oxide fuel cells (SOFCs), the oxygen electrode of reversible solid oxide fuel cells (RSOCs), the catalyst for low-temperature electrolysis of water, and the electrode of supercapacitors, etc.; the synergistic effect of the nano-catalyst and the Ca x Co4O 9+δ matrix enables the material to have good catalytic activities for oxygen evolution and oxygen reduction reactions. The present invention has the advantages of simple operation, low cost, and being conducive to mass production, and has good application prospects in the fields of medium and high-temperature fuel cells and low-temperature catalysis.

Description

Technical Field

[0001] The present invention relates to the fields of solid oxide fuel cells, solid oxide electrolytic cells and supercapacitors, and in particular to a Ca2+ / Ca ... x Co 4 O 9+δ Materials and applications. Background Art

[0002] At present, we are facing three crises: resource shortage, environmental pollution and ecological system imbalance. The development and utilization of efficient clean energy is an effective way to solve the problems of environmental pollution and energy shortage. Reversible solid oxide cells (RSOCs) are a kind of all-solid-state device with two working modes. The fuel cell (SOFC) mode directly converts the chemical energy stored in the fuel into electrical energy for power generation, and the electrolyzer (SOEC) mode produces H by electrolyzing water. 2 Convert electrical energy into chemical energy. When the SOFC and SOEC modes are alternately operated, a cycle of power generation and hydrogen production can be achieved, which is of great significance for solving the energy problems faced by human society. The main structure of RSOCs includes oxygen electrode, fuel electrode and electrolyte. The oxygen electrode is an important component of RSOCs. It needs to have good catalytic activity for oxygen reduction reaction and precipitation reaction, and have good matching with electrolyte materials. At the same time, it also needs to have high electronic and ionic conductivity to provide a place for the electrochemical reaction of oxygen. Layered Ca 3 Co 4 O 9+δ The material has remarkable thermal and chemical stability at high temperatures, its thermal expansion coefficient matches that of most electrolyte materials, and has high electrical conductivity (100 S·cm -1 , 700 ℃) and excellent surface oxygen exchange capacity ( k * = 1.6 × 10 -7 cm·s -1 , 700 ℃), considering the development trend of medium and low temperature of solid oxide batteries and the matching between battery components, the layered structure of CaxCo4O9+δ material is widely used in the cathode of SOFC and the oxygen electrode of RSOCs. 3 Co 4 O 9+δ The research on electrodes mainly focuses on the composite with electrolyte materials and the doping of A-site and B-site elements, while the research on Ca 3 Co 4 O 9+δ There are few studies on nanocatalyst modification and microstructure modification of electrodes.

[0003] So far, nanoparticle in-situ precipitation technology has been mainly applied to ABO 3In perovskite oxides, easily reducible metal particles are precipitated from the B site through vacancy at the A site and doping at the B site. Since this precipitation process needs to be carried out under reducing conditions, in-situ precipitated nanoparticles are mainly used in the anode of SOFC and the hydrogen electrode of reversible batteries. The application of in-situ precipitation technology in the cathode and oxygen electrode is very rare. Summary of the invention

[0004] The present invention overcomes the shortcomings of the prior art and provides a Ca2+ nanocatalytic particle in-situ precipitation method. x Co 4 O 9+δ Materials and applications.

[0005] The present invention develops and designs a kind of Ca2+ nano-catalytic particles in situ precipitation under air atmosphere. x Co 4 O 9+δ Electrode materials, through a simple non-stoichiometric method in Ca 3 Co 4 O 9+δ In-situ dissolution of Co on the material surface 3 O 4 or Ca(OH) 2 Catalytic nanoparticles further increase Ca x Co 4 O 9+δ The electrode has catalytic activity for oxygen evolution and oxygen reduction reactions. Since the preparation process of this method is simple and does not require a reducing atmosphere, the preparation cost is reduced compared to other in-situ precipitation techniques, making it more cost-effective and practical.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a Ca2+ nanocatalytic particle in situ precipitation x Co 4 O 9+δ The material is Ca x Co 4 O 9+δ Annealing in air to achieve Ca 3 Co 4 O 9+δ Surface Co 3 O 4 or Ca(OH) 2 Materials for in-situ precipitation of catalytic nanoparticles, wherein 1≤x≤5.

[0007] Furthermore, when Ca x Co 4 O 9+δ When 1≤x<3, Co is precipitated in situ under high temperature annealing conditions. 3 O 4 Nanocatalytic particles, when Ca x Co4 O 9+δ When 3 < x ≤ 5, Ca(OH) precipitates in situ under high-temperature annealing conditions 2 nano-catalytic particles; the high-temperature annealing temperature is 800°C - 1000°C, and the annealing time is 5 - 20 hours.

[0008] Furthermore, Ca is obtained by Ni doping x Co y Ni 4-y O 9+δ materials, where 1 ≤ x ≤ 3, 0 ≤ y ≤ 0.1, and the Ca x Co y Ni 4-y O 9+δ material is annealed in air to achieve in-situ dissolution of metal oxide nanoparticles on the material surface.

[0009] Furthermore, the preparation method of the Ca x Co 4 O 9+δ is sol-gel method, glycine combustion method or solid-phase method.

[0010] Furthermore, the sol-gel method for preparing Ca x Co 4 O 9+δ material with in-situ precipitated nano-catalytic particles includes the following steps:

[0011] (1) According to a specific stoichiometric ratio, dissolve Ca(NO 3 ) 2 ·4H 2 O and Co(NO 3 ) 2 ·6H 2 O in deionized water, and add citric acid as a complexing agent, where the molar ratio of citric acid to metal ions is 1.5:1;

[0012] (2) Continuously stir the obtained mixed solution in a water bath at 80°C until a viscous purple-red gel is obtained;

[0013] (3) Dry the obtained gel in an oven at 200°C for 12 hours to completely dry the gel and obtain a fluffy xerogel;

[0014] (4) Grind the obtained xerogel thoroughly in a mortar until it is completely and evenly mixed;

[0015] (5) Calcinate the ground product at 800°C - 1000°C for 5 - 20 hours to obtain Ca x Co 4 O 9+δpowder.

[0016] The present invention also provides the above-mentioned in-situ precipitation of nano-catalytic particles Ca x Co 4 O 9+δ The material is used in preparing the cathode of a solid oxide fuel cell, the anode of a solid oxide electrolyzer or the oxygen electrode of a reversible solid oxide fuel cell.

[0017] Further, the above application comprises the following steps: Ca x Co 4 O 9+δ The material powder is mixed with an organic binder and a pore-forming agent and ground into an electrode slurry, and the slurry is uniformly deposited, cast or coated on the surface of the electrolyte, and calcined at a high temperature to form a porous electrode; the calcination temperature is 800° C.-1000° C., and the calcination time is 2-10 hours;

[0018] The electrolyte is LaGaO doped with Mg and Sr 3 (LSGM), gadolinium oxide doped ceria (GDC), samarium oxide doped ceria (SDC) oxygen ion conducting electrolyte, or yttria stabilized zirconia (YSZ) electrolyte with the above electrolytes added as an isolation layer, or BaCeO 3 Base, SrCeO 3 Base, SrZrO 3 base and BaZrO 3 A matrix electron conductive electrolyte; a certain proportion of electrolyte powder can also be mixed into the electrode slurry.

[0019] The present invention also provides the above-mentioned in-situ precipitation of nano-catalytic particles Ca x Co 4 O 9+δ Application of materials in the preparation of supercapacitor electrodes.

[0020] Furthermore, the Ca x Co 4 O 9+δ The material powder and the binder are dissolved in anhydrous ethanol and ultrasonically dispersed for 20-30 minutes to obtain a uniform suspension. The carbon paper current collector is immersed in the suspension to dip the electrode active material, and the dipping is repeated multiple times. After that, the electrode is dried at 80°C for 2-12 hours to remove the binder to obtain the electrode of the supercapacitor. The carbon paper current collector can also be foamed nickel.

[0021] The present invention also provides the above-mentioned in-situ precipitation of nano-catalytic particles Ca x Co 4 O 9+δ Application of materials in the preparation of self-supporting supercapacitor electrodes.

[0022] Furthermore, Ca x Co 4 O 9+δ The material powder is mixed with a pore-forming agent, placed in a mold for tableting, and then sintered in an air atmosphere to obtain Ca x Co 4 O 9+δ Self-supporting electrode.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Compared with the electrode covered with nanocatalytic particles prepared by the solution impregnation method, the present invention avoids the process of repeated impregnation and calcination, simplifies the preparation process, saves preparation time, and the nanoparticles precipitated in situ form a nested structure with the substrate, and the precipitated particles are more evenly distributed, avoiding the problem of sintering and agglomeration of nanoparticles existing in the solution impregnation method.

[0025] 2. The existing in-situ precipitation technology is mainly used in the anode of the fuel cell. It requires reducing conditions to achieve the precipitation of nanoparticles. It is rarely used in the cathode. Alternatively, the material is first placed in a reducing atmosphere to precipitate metal nanoparticles, and then the metal particles are converted into metal oxides in an oxidizing atmosphere to obtain cathode materials covered with oxide nanoparticles. Compared with precipitation under a reducing atmosphere, the present invention achieves in-situ precipitation of nanocatalytic particles in a simple air atmosphere, which is more time- and cost-effective.

[0026] 3. With Ca x Co 4 O 9+δ Compared with the materials, the Ca x Co 4 O 9+δ The material has higher catalytic activity for oxygen evolution and oxygen reduction reactions. Applying it to the cathode of solid oxide fuel cells, the anode of solid oxide electrolyzers, and the oxygen electrode of reversible solid oxide fuel cells can further improve the output performance of the battery and increase the energy conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is Ca in Examples 1 and 2 of the present invention 1.5 Co 4 O 9+δ and Ca 3.5 Co 4 O 9+δ XRD pattern of

[0028] Figure 2 In the present invention, Ca x Co 4O 9+δ Impedance spectrum of the half-cell corresponding to the A-site vacancy material;

[0029] Figure 3 is the power density curve of a single cell in SOFC mode in Example 1 of the present invention;

[0030] Figure 4 is the output performance curve of a single cell in SOEC mode in Example 1 of the present invention;

[0031] Figure 5 is the hydrogen production rate of the electrolytic cell in Example 1 of the present invention;

[0032] Figure 6 In the present invention, Ca x Co 4 O 9+δ Impedance spectrum of the half-cell corresponding to the A-site rich material. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific embodiments. Example 1

[0034] According to the synthesis of 0.01 mol Ca 1.5 Co 4 O 9+δ 3.5423 g of calcium nitrate and 11.6412 g of cobalt nitrate powder were weighed and dissolved in deionized water, and 17.33655 g of citric acid was added as a complexing agent, wherein the molar ratio of citric acid to metal ions was 1.5:1;

[0035] The resulting precursor solution was continuously stirred in a water bath at 80°C to obtain a viscous purple-red jelly;

[0036] The obtained jelly was dried in a drying oven at 200°C for 12 hours to completely dry the jelly to obtain a fluffy xerogel;

[0037] The resulting powder is thoroughly ground in a mortar until it is completely mixed;

[0038] The ground product was calcined at 850 °C for 10 h to obtain Ca 1.5 Co 4 O 9+δ powder;

[0039] Ca 1.5 Co 4 O 9+δ The powder, organic binder (92% pineol and 8% ethyl cellulose) and pore former were mixed in a mass ratio of 5:5:1 and ground in an agate mortar for 2 h to obtain a well-mixed electrode slurry;

[0040] Ca 1.5 Co 4 O 9+δ The slurry was coated on YSZ electrolyte with GDC as separator as working electrode (WE) and sintered at 850 °C for 10 h;

[0041] Silver paste (DAD-87, Shanghai Synthetic Resin Research Institute, China) was applied on the other side of the YSZ electrolyte support as the counter electrode (CE), which was symmetrical to the working electrode. The silver reference electrode (RE) was located on the same side of the oxygen electrode and kept a certain distance from the oxygen electrode to obtain an effective area of ​​0.26 cm 2 The polarization resistance and polarization overpotential of the half-cell are tested by the three-electrode method.

[0042] Ni-YSZ was selected as the hydrogen electrode of RSOCs, and a hydrogen electrode-supported Ni-YSZ / YSZ / GDC / CCO single cell was prepared;

[0043] The single cell was sealed in an alumina ceramic tube for electrochemical performance testing. Before the test, NiO was reduced to Ni in hydrogen at 650 °C. In SOFC mode, the flow rate was 50 mL min -1 Wet H 2 (3% H 2 O) is transferred to the Ni-YSZ electrode, and the oxygen electrode is exposed to the air atmosphere. In the SOEC mode, water vapor, H 2 and Ar mixed gas is transported to the Ni-YSZ electrode, where H 2 The gas volume ratio of Ar was 75:25, and the total flow rate was 100 ml min -1 .

[0044] The Ca obtained in Example 1 1.5 Co 4 O 9+δ The oxygen electrode materials were characterized by XRD, such as Figure 1 As shown, the in-situ precipitation of Co 3 O 4 Nanocatalytic Ca 3 Co 4 O 9+δ Powder.

[0045] The electrochemical output performance of the oxygen electrode and the battery were tested at 650°C-800°C using a CHI660E electrochemical workstation (CH Instrument Co., Ltd., Shanghai, China) for the half-cell and single cell obtained in Example 1. 1.5 Co 4 O 9+δ The polarization resistance of the half-cell is 0.091 Ω·cm2 ( Figure 2 ), and Ca 3 Co 4 O 9+δ In comparison, Ca 1.5 Co 4 O 9+δ The polarization resistance of the electrode is significantly reduced, and the in-situ precipitation of nanoparticles improves the catalytic activity of the electrode. The maximum power density of the single cell at 800°C is 479 mW cm -2 ( Figure 3 ), the electrolysis current density at an electrolysis voltage of 1.4 V is 1236 mA·cm -2 ( Figure 4 ), the hydrogen production rate of the electrolytic cell is as follows Figure 5 shown. Example 2

[0046] 0.01 mol Ca 3.5 Co 4 O 9+δ Synthesis and electrochemical performance testing.

[0047] According to the synthesis of 0.01 mol Ca 3.5 Co 4 O 9+δ 8.26525 g of calcium nitrate and 11.6412 g of cobalt nitrate powder were weighed and dissolved in deionized water to form a mixed solution;

[0048] 8.445375 g of glycine was added to the mixed solution as a complexing agent, wherein the molar ratio of glycine to metal ions was 1.5:1;

[0049] The obtained precursor solution was placed on a heated magnetic stirrer and stirred continuously at 100°C until a viscous purple-red jelly was formed;

[0050] The temperature of the heating stage is further increased to 400°C-500°C, so that the colloid spontaneously ignites to obtain a precursor powder;

[0051] The obtained precursor powder was thoroughly ground in a mortar until it was completely mixed;

[0052] 6) Calcinate at 850℃ for 10 hours to obtain Ca 3.5 Co 4 O 9+δ powder;

[0053] 7) Prepare an electrode according to steps 6) to 8) of Example 1.

[0054] The Ca obtained in Example 2 3.5 Co 4 O9+δ The materials were characterized by XRD, such as Figure 1 As shown, the in situ precipitation of Ca(OH) 2 Nanocatalytic Ca 3 Co 4 O 9+δ Powder.

[0055] The performance of the oxygen electrode obtained in Example 2 was tested. At 800°C, Ca 3.5 Co 4 O 9+δ The polarization resistance of the oxygen electrode is 0.1352 Ω·cm 2 ( Figure 6 ), and Ca 3 Co 4 O 9+δ In comparison, Ca 3.5 Co 4 O 9+δ The polarization resistance of the electrode is significantly reduced, and the in-situ precipitation of nanoparticles significantly improves the catalytic activity of the electrode.

[0056] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any modifications within the present invention should be included in the protection scope of the present invention.

Claims

1. A Ca2+ nanoparticle precipitated in situ x Co 4 O 9+δ Material, It is characterized in that is composed of Ca x Co 4 O 9+δ Annealing in air realizes in-situ precipitation of catalytic nanoparticles of Ca 3 Co 4 O 9+δ Surface Co 3 O 4 or Ca(OH) 2 The material that catalyzes the in-situ precipitation of nanoparticles. When 1 ≤ x < 3 in Ca x Co 4 O 9+δ Co 3 O 4 nanocatalytic particles are in-situ precipitated under high-temperature annealing conditions. When 3 < x ≤ 5 in Ca x Co 4 O 9+δ Ca(OH) 2 nanocatalytic particles are in-situ precipitated under high-temperature annealing conditions; the high-temperature annealing temperature is 800 °C - 1000 °C, and the annealing time is 5 - 20 hours.

2. The Ca2+ nanocatalytic particles prepared in situ according to claim 1 x Co 4 O 9+δ Material, It is characterized in that The Ca x Co 4 O 9+δ The preparation method is sol-gel method, glycine combustion method or solid phase method.

3. The Ca2+ nanocatalytic particles prepared in situ according to claim 2 x Co 4 O 9+δ Material, It is characterized in that The sol-gel method is used to prepare Ca2+ nanocatalytic particles in situ. x Co 4 O 9+δ Materials, including the following steps: (1) According to a specific stoichiometric ratio, Ca(NO 3 ) 2 ·4H 2 O and Co(NO 3 ) 2 6H 2 O was dissolved in deionized water, and citric acid was added as a complexing agent, wherein the molar ratio of citric acid to metal ions was 1.5:1; (2) The obtained mixed solution is continuously stirred in a water bath at 80°C until a viscous purple-red jelly is obtained; (3) drying the obtained colloid in a drying oven at 200°C for 12 hours to completely dry the colloid to obtain a fluffy xerogel; (4) Grind the obtained dry gel in a mortar until it is completely mixed; (5) calcining the ground product at 800°C-1000°C for 5-20 hours to obtain Ca2+ nanocatalytic particles precipitated in situ. x Co 4 O 9+δ powder.

4. A Ca in situ precipitated nanocatalytic particles as claimed in any one of claims 1 to 3 x Co 4 O 9+δ The material is used in preparing the cathode of a solid oxide fuel cell, the anode of a solid oxide electrolyzer or the oxygen electrode of a reversible solid oxide fuel cell.

5. The use according to claim 4, It is characterized in that Ca x Co 4 O 9+δ The material powder is mixed with an organic binder and a pore-forming agent and ground into an electrode slurry, and the slurry is uniformly deposited, cast or coated on the surface of the electrolyte, and calcined at a high temperature to form a porous electrode; the calcination temperature is 800° C.-1000° C., and the calcination time is 2-10 hours; The electrolyte is LaGaO doped with Mg and Sr 3 , gadolinium oxide doped cerium oxide, samarium oxide doped cerium oxide oxygen ion conductive electrolyte, or yttria stabilized zirconia electrolyte with the above electrolyte added as an isolation layer on the surface, or BaCeO 3 Base, SrCeO 3 Base, SrZrO 3 base and BaZrO 3 A matrix electron conductive electrolyte; a certain proportion of electrolyte powder can also be mixed into the electrode slurry.

6. A Ca-based nanocatalytic particle precipitated in situ as claimed in any one of claims 1 to 3 x Co 4 O 9+δ Application of materials in the preparation of supercapacitor electrodes.

7. The use according to claim 6, It is characterized in that Ca x Co 4 O 9+δ The material powder and the binder are dissolved in anhydrous ethanol and ultrasonically dispersed for 20-30 minutes to obtain a uniform suspension. The carbon paper current collector is immersed in the suspension to dip the electrode active material, and the dipping is repeated multiple times. After that, the electrode is dried at 80°C for 2-12 hours to remove the binder to obtain the electrode of the supercapacitor. The carbon paper current collector can also be foamed nickel.

8. A Ca-based nanocatalytic particle precipitated in situ as claimed in any one of claims 1 to 3 x Co 4 O 9+δ Application of materials in the preparation of self-supporting supercapacitor electrodes, It is characterized in that Ca x Co 4 O 9+δ The material powder is mixed with a pore-forming agent, placed in a mold for tableting, and then sintered in an air atmosphere to obtain Ca x Co 4 O 9+δ Self-supporting electrode.

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