Preparation method of praseodymium copper oxide nanoparticles based on high-temperature self-propagating combustion

Abstract

The invention relates to a preparation method of praseodymium copper oxide nanoparticles based on high-temperature self-propagating combustion, in particular to a composite process combining a polyethylene glycol assisted sol-gel method and a self-propagating combustion technology. According to the method, firstly, polyethylene glycol serves as a complexing agent and a structure regulating agent, a precursor is guided to form a stable sol system, then a self-propagating combustion reaction is initiated under the control condition, the precursor is effectively promoted to be rapidly converted into an intermediate product, and finally PCO nano-particles with smaller grain size and higher dispersity are obtained through high-temperature calcination treatment. The prepared material is more uniform in particle size and better in crystallinity, has the advantages of larger specific surface area and potential catalytic / electrochemical performance, and is suitable for the fields of electrode materials, catalyst carriers and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic functional material preparation, and in particular to a method for preparing a PCO nanomaterial. The method is a cross-application of a sol-gel method, a self-propagating combustion method, and nanomaterial engineering technology, and is suitable for catalysis, energy storage, and other energy and environment-related fields. Background Art

[0002] Perovskite-like composite oxides (A2BO4) are considered to be a superstructured composite oxide composed of a combination of perovskite building blocks (ABO3) and other building blocks (AO). Pr2CuO4, a typical perovskite-like composite oxide, is a rare earth cuprate material with a K2NiF4-type crystal structure. Its unique electronic structure and physicochemical properties have shown significant application potential in high-temperature superconductivity, magnetic materials, catalysis, and sensors. As a typical T'-phase copper oxide, Pr2CuO4 exhibits unique antiferromagnetism and electron correlation effects, and its electronic state can be manipulated by carrier doping. Due to its excellent electrochemical performance, Pr2CuO4 is considered a potential functional material in solid oxide electrolytic cells (SOECs). However, existing preparation methods often result in large Pr2CuO4 particles, which limit their interfacial reactivity and ion transport efficiency in SOECs. Reducing the particle size not only increases the material's specific surface area and enhances interfacial reaction kinetics, but also effectively improves its stability and conductivity in high-temperature electrochemical environments. Therefore, exploring new methods for the controllable synthesis of Pr2CuO4 nanomaterials with smaller particle size and uniform structure is of great significance for improving their practical application performance in SOEC systems.

[0003] The preparation methods for PCO nanomaterials primarily include solid-state reaction, sol-gel, hydrothermal / solvothermal, and pulsed laser deposition. Currently, Pr2CuO4 nanomaterials are primarily prepared using solid-state reaction, sol-gel, hydrothermal / solvothermal, and pulsed laser deposition methods. However, these methods still suffer from low product purity, uneven grain size, uncontrollable morphology, complex processes, and high costs. For example, the solid-state reaction method requires high-temperature calcination (>900°C), which can easily lead to volatilization of the Pr / Cu elements and non-stoichiometric ratios; the sol-gel method is prone to introducing carbon residues, which can affect the conductivity of the material; and while the hydrothermal method can lower the synthesis temperature, it can easily lead to stacking of nanosheets and poor batch stability. To address these shortcomings, the present invention aims to develop a simple, low-cost method for preparing Pr2CuO4 nanomaterials that can precisely control the structure and properties. Summary of the Invention

[0004] To overcome the above-mentioned deficiencies of the prior art, the present invention provides a method for preparing PCO materials with improved particle size control, providing a method for preparing PCO nanomaterials with smaller particle size, better dispersibility, and superior crystallinity, thereby solving the problems of large product particle size, severe agglomeration, and difficult reaction process control in existing preparation methods.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A method for preparing praseodymium copper oxide nanoparticles based on high-temperature self-propagating combustion comprises the following steps:

[0007] s1. Polyethylene glycol gel method: Mix the nitrate solutions of the metals in stoichiometric proportions, add citric acid for complexation, stir until clear, and then place in an oil bath at 75-85°C. Evaporate the solution to 20-40% of the original volume, then slowly add polyethylene glycol 20,000 while stirring. Continue stirring for 110-130 minutes until the solution forms a gel.

[0008] s2, self-propagating combustion stage: The obtained gel is continuously heated until a self-propagating combustion reaction is initiated, quickly forming a precursor powder; before combustion, a strong white smoke with a pungent odor is produced, and during combustion, a bright green flame is produced, and after combustion, a black powder with uniform particles is formed;

[0009] s3. High-temperature calcination stage: The product obtained by self-propagating combustion is calcined at 900-950 °C in an air atmosphere for 9-11 h to obtain PCO nanoparticles.

[0010] In s1, the molar ratio of the nitrate to the citric acid is 1:1-2, the molar ratio of praseodymium nitrate to copper nitrate in the nitrate is 1-3:1, the amount of polyethylene glycol 20000 is 1-2 times the sum of the weight of the nitrate and the citric acid, the lanthanum source is a hexahydrate nitrate compound, the copper source is a trihydrate nitrate compound, the citric acid is of analytical grade, and the solvent used in the process is deionized water.

[0011] Furthermore, as an optimization scheme, in the aforementioned method for preparing praseodymium copper oxide nanoparticles based on high-temperature self-propagating combustion, the high-temperature calcination stage is specifically to increase the temperature to 900-950°C at a heating rate of 5°C / min and keep it for 9-11 hours in an air atmosphere, or first increase the temperature to 200-400°C at a heating rate of 2-3°C / min and keep it for 3 hours, and then increase the temperature to 900-950°C at a heating rate of 3-10°C / min and keep it for 6-8 hours.

[0012] Furthermore, as an optimization solution, in the aforementioned method for preparing praseodymium copper oxide nanoparticles based on high-temperature self-propagating combustion, the particle size of the PCO nanoparticles is 75-90 nm.

[0013] Furthermore, as an optimization solution, in the aforementioned method for preparing praseodymium copper oxide nanoparticles based on high-temperature self-propagating combustion, during the self-propagating combustion stage, the obtained gel is placed in a cassette furnace for heating.

[0014] Furthermore, as an optimization solution, in the aforementioned method for preparing praseodymium copper oxide nanoparticles based on high-temperature self-propagating combustion, during the high-temperature calcination stage, the product obtained by the self-propagating combustion is placed in a muffle furnace for calcination.

[0015] Compared with the prior art, the above-mentioned technical solution of the present invention has achieved the following significant progress: the present invention significantly reduces the particle size of the PCO material and increases the specific surface area of the material through the synergistic effect of the polyethylene glycol-assisted sol-gel method and the high-temperature self-propagating combustion method, providing more active sites for catalytic and electrochemical applications. Self-propagating combustion provides instantaneous high-temperature reaction conditions, allowing the precursor to be quickly converted into highly crystalline nanoparticles, avoiding problems such as uneven particles and uncontrolled growth that may occur in traditional calcination. Compared with traditional single sol-gel or combustion synthesis processes, the process route of the present invention is simple, does not require complex equipment, has a short reaction time, low energy consumption, and is easy to prepare on a large scale. The prepared PCO nanomaterial exhibits good electrochemical activity due to its excellent electrical conductivity and low polarization impedance, making it suitable for high-temperature electrochemical devices such as solid oxide fuel cell cathodes, oxygen reduction catalysis, and electrochemical sensors. In application tests, it has demonstrated stable electrochemical performance and low interfacial impedance, that is, it has good electrical conductivity, thermal stability, and interfacial catalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the X-ray diffraction pattern of the Pr2CuO4 material in Example 1.

[0017] Figure 2 This is the IV curve of the Pr2CuO4 material in Example 1.

[0018] Figure 3 This is the electrochemical impedance spectrum of the Pr2CuO4 material in Example 1.

[0019] Figure 4 This is the particle size diagram of the Pr2CuO4 material in Example 1. DETAILED DESCRIPTION

[0020] The following is a further description of specific embodiments of the present invention. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0021] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0022] Example 1: In-situ preparation and characterization of Pr2CuO4 materials

[0023] The specific preparation steps are as follows:

[0024] 1. Using deionized water as the reaction medium, a mixed metal salt solution was prepared by accurately weighing 19.33 g of praseodymium nitrate hexahydrate (Pr(NO3)3·6H2O) and 5.37 g of copper nitrate trihydrate (Cu(NO3)2·3H2O) in the stoichiometric ratio of Pr2CuO4. Under continuous magnetic stirring, 6.4 g of citric acid was added to the mixed solution as a complexing agent. Subsequently, 80 mL of the reaction solution was concentrated in an 80°C oil bath. When the solution volume was reduced to approximately 40 mL, 20 g of polyethylene glycol 20000 was slowly added as a dispersant while maintaining stirring. Stirring was continued for 120 minutes to ensure thorough mixing. This preparation process maintained strict control of the reaction temperature and addition rate, providing a stable precursor system for the subsequent sol-gel transition.

[0025] 2. The homogeneous gel obtained in step 1 is dried and placed in a high-temperature cassette furnace and heated until spontaneous combustion to obtain a nano-scale precursor powder with a porous structure.

[0026] 3. The precursor powder from step 2 was placed in a muffle furnace and subjected to high-temperature crystallization under static air conditions. Using programmed temperature control, the temperature was increased from room temperature to a target temperature of 950°C at a rate of 5°C / min and maintained at this temperature for 10 hours to ensure sufficient crystal growth and impurity decomposition. After calcination, the sample was allowed to cool naturally to room temperature in the furnace, ultimately yielding PCO nanoparticles with uniform particle size and excellent crystallinity.

[0027] 4. Pr2CuO4 material characterization

[0028] (1) Phase analysis:

[0029] The Pr2CuO4 nanoparticles in step 3 were subjected to X-ray diffraction analysis, and the spectrum was as follows: Figure 1 As shown in the figure, each diffraction peak is attributed to Pr2CuO4 (PDF#79-0957), without other impurity peaks, and the diffraction peaks are sharp and the peak positions are not shifted, which indicates that Pr2CuO4 material is obtained.

[0030] (2) Electrochemical analysis:

[0031] Battery Assembly: The assembly of an electrolytic cell for electrochemical testing can be divided into three steps: pressing the electrolyte sheet, brushing the buffer layer and electrodes, and assembling the three-electrode system. The SDC electrolyte substrate is prepared primarily by dry pressing. 1.2 g of the prepared SDC powder is mixed with a PVA binder (5 wt% polyvinyl alcohol + 95 wt% water) and ground evenly. The mixture is then placed in a stainless steel tablet press. A tablet press applies a pressure of 16 MPa to produce an electrolyte substrate with a diameter of 20 mm. The substrate is then fired in a muffle furnace at 1400°C for 4 h to obtain a dense electrolyte substrate. Finally, the fired SDC substrate is polished with sandpaper (400 and 2000 mesh) to a thickness of approximately 0.75 mm to ensure the consistency of the electrolyte sheet. To prevent potential side reactions between the electrolyte and fuel electrode materials at high temperatures, GDC was uniformly mixed with an organic binder (6 wt% cellulose dissolved in 94 wt% terpineol). The GDC slurry was screen-printed onto one side of the SDC electrolyte. This was then sintered at 1400°C for 2 hours to create an SDC electrolyte sheet with a GDC buffer layer. Next, Ni-YSZ powder was uniformly mixed with the organic binder in the desired proportions. The screen-printing process was repeated, and the electrode slurry was applied to the GDC buffer layer and heat-treated at 1300°C for 3 hours to produce a Ni-YSZ composite half-cell. PCO nanoparticles were then treated in the same manner, ultimately resulting in a full cell with Ni-YSZ as the cathode and PCO as the anode.

[0032] Figure 2 The IV curve obtained for the Pr2CuO4 nanoparticle anode battery test shows that it can reach 1.18 A / cm at a voltage of 1.3 V. 2 , anode materials with smaller particle sizes can significantly increase the specific surface area of the reaction, which makes there more active sites for ion transport per unit volume.

[0033] Figure 3 This is the electrochemical impedance spectrum of the Pr2CuO4 nanoparticle anode battery test. The polarization resistance of the half-cell was calculated by fitting the impedance diagram. At 750 ℃, the polarization resistance can reach 0.31 Ω·cm 2 The extremely small polarization resistance indicates that the nanoparticles have a fast oxygen diffusion rate and good ionic and electronic conductivity.

[0034] (3) Particle size analysis:

[0035] Figure 4 The strongest diffraction peak (2≈32.5°) was selected to calculate the full width at half maximum (FWHM), and the Scherrer formula was used to calculate the full width at half maximum (FWHM). Estimate the grain size. Where, is the shape factor (taken as 0.9), Cu- Ray wavelength (0.15406 nm), is the half-height width of the peak in radians, The calculated results show that the average grain size of the prepared sample is about 83.8 nm, indicating that the material prepared by this method has a smaller particle size and a more uniform distribution, which is beneficial to improving the specific surface area and interfacial reaction activity of the material.

[0036] Example 2: Pr2Cu 0.5 Mg 0.5 In situ preparation and characterization of O4 materials

[0037] The preparation method is the same as that in Example 1, except that: in step 1, a magnesium salt is added at the B site, wherein the molar ratio of copper salt to magnesium salt is 1:1, and the total molar ratio of copper salt to magnesium salt in the material is 1; steps 2 and 3 are the same as those in Example 1. 0.5 Mg 0.5 The results of the characterization of the O4 powder morphology are similar to those of Example 1, with only a new peak of magnesium added in the XRD pattern; the polarization resistance data and stability of the electrochemical analysis are similar to those of Example 1, and the powder also has the advantages of fast oxygen diffusion rate, good ionic and electronic conductivity, and stable electrochemical performance. 0.5 Mg 0.5 The polarization resistance of SOEC with O4 powder as anode is 0.08 Ω, and the current density at 1.3 V is 1.26 A / cm 2 。

[0038] Example 3: Pr2Cu 0.3 Mg 0.7 In situ preparation and characterization of O4 materials

[0039] The preparation method is the same as that of Example 1, except that: in step 1, magnesium salt is added at the B site, wherein the molar ratio of copper salt to magnesium salt is 0.3:0.7, and the total molar ratio in the material is 1; steps 2 and 3 are the same as those of Example 1. 0.3 Mg 0.7 The results of the characterization of the O4 powder morphology are similar to those of Example 1, with only a new peak of magnesium added in the XRD pattern; the polarization resistance data and stability of the electrochemical analysis are similar to those of Example 1, and the powder also has the advantages of fast oxygen diffusion rate, good ionic and electronic conductivity, and stable electrochemical performance. 0.3 Mg 0.7 The polarization resistance of SOEC with O4 powder as anode is 0.09 Ω, and the current density at 1.3 V is 1.07 A / cm 2 。

[0040] Example 4: Pr2Cu 0.7 Mg 0.3 In situ preparation and characterization of O4 materials

[0041] The preparation method is the same as that of Example 1, except that: in step 1, magnesium salt is added at the B site, wherein the molar ratio of copper salt to magnesium salt is 0.7:0.3, and the total molar ratio in the material is 1; steps 2 and 3 are the same as those of Example 1. 0.7 Mg 0.3 The results of the characterization of the O4 powder morphology are similar to those of Example 1, with only a new peak of magnesium added in the XRD pattern; the polarization resistance data and stability of the electrochemical analysis are similar to those of Example 1, and the powder also has the advantages of fast oxygen diffusion rate, good ionic and electronic conductivity, and stable electrochemical performance. 0.7 Mg 0.3 The polarization resistance of SOEC with O4 powder as anode is 0.1 Ω, and the current density at 1.3 V is 1.304 A / cm 2 .

[0042] The above general description of the invention and the description of its specific embodiments involved in this application should not be construed as limiting the technical solutions of the invention. Based on the disclosure of this application, those skilled in the art may, without violating the constituent elements of the invention involved, add to, subtract from, or combine the disclosed technical features in the above general description and / or specific embodiments (including examples) to form other technical solutions within the scope of protection of this application.

Claims

1. A method for preparing praseodymium copper oxide nanoparticles based on high-temperature self-propagating combustion, characterized in that: The following steps are involved: s1. Polyethylene glycol gel method: Mix the nitrate solutions of the metals in stoichiometric proportions, add citric acid for complexation, stir until clear, and then place in an oil bath at 75-85°C. Evaporate the solution to 20-40% of the original volume, then slowly add polyethylene glycol 20,000 while stirring. Continue stirring for 110-130 minutes until the solution forms a gel. s2, self-propagating combustion stage: the obtained gel is continuously heated until a self-propagating combustion reaction is initiated, and a precursor powder is quickly formed; s3. High-temperature calcination stage: The product obtained by self-propagating combustion is calcined at 900-950 °C in an air atmosphere for 9-11 h to obtain PCO nanoparticles.

2. The method for preparing praseodymium copper oxide nanoparticles based on high temperature self-propagating combustion method according to claim 1, characterized in that: In s1, the molar ratio of the nitrate to the citric acid is 1:1-2, the molar ratio of praseodymium nitrate to copper nitrate in the nitrate is 1-3:1, the amount of polyethylene glycol 20000 is 1-2 times the sum of the weight of the nitrate and the citric acid, wherein the lanthanum source is a hexahydrate nitrate compound, the copper source is a trihydrate nitrate compound, the citric acid is of analytical grade, and the solvent used in the process is deionized water.

3. The method for preparing praseodymium copper oxide nanoparticles based on high temperature self-propagating combustion method according to claim 1, characterized in that: The high temperature calcination stage is specifically to raise the temperature to 900-950° C. at a heating rate of 5° C. / min under air atmosphere and keep the temperature for 9-11 hours.

4. The method for preparing praseodymium copper oxide nanoparticles based on high temperature self-propagating combustion method according to claim 1, characterized in that: The high temperature calcination stage is specifically to heat the material to 200-400°C at a heating rate of 2-3°C / min and keep the temperature for 3 hours in air atmosphere, and then heat the material to 900-950°C at a heating rate of 3-10°C / min and keep the temperature for 6-8 hours.

5. The method for preparing praseodymium copper oxide nanoparticles based on high temperature self-propagating combustion according to claim 1, characterized in that: The particle size of the PCO nanoparticles is 75-90 nm.

6. The method for preparing praseodymium copper oxide nanoparticles based on high temperature self-propagating combustion according to any one of claims 1 to 5, characterized in that: In the self-propagating combustion stage, the obtained gel is placed in a cassette furnace for heating.

7. The method for preparing praseodymium copper oxide nanoparticles based on high temperature self-propagating combustion according to any one of claims 1 to 5, characterized in that: In the high-temperature calcination stage, the product obtained by self-propagating combustion is placed in a muffle furnace for calcination.

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