Preparation method of nano cerium oxide, and prepared material and application thereof

Abstract

The application discloses a preparation method of nano cerium oxide. The method comprises the following steps: placing BaCeO3 powder in a heating furnace, purging the heating furnace with inert gas, then introducing carbon dioxide into the heating furnace, and then heating to 500-1000 DEG C and continuously reacting for 6-12 hours, cooling to room temperature, removing BaCO3 generated in the reaction by using acid and completely volatilizing the carbon dioxide, and then filtering and drying to obtain nano CeO2. The cerium oxide particles prepared by the method are in nanometer level, uniform in particle size, free of agglomeration, and good in conductivity, and the method is simple in operation and low in cost.

Description

Technical Field

[0001] This invention relates to the preparation of nanomaterials, specifically to a method for preparing nano-cerium oxide, the prepared material, and its applications. Background Technology

[0002] Cerium oxide is a ceramic material with a stable fluorite structure. Its crystal structure remains unchanged from room temperature to its melting point, making it suitable for use as a catalyst, electronic ceramic, and electrolyte. It has wide applications in semiconductors, fuel cells, and luminescent materials. The performance of CeO2 is closely related to its particle size; nano-sized cerium oxide exhibits superior material properties. Traditional solid-phase synthesis methods result in larger particle sizes, while liquid-phase synthesis methods, such as gel synthesis, have a certain probability of powder agglomeration, and nitrate raw materials are relatively expensive. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing nano-cerium oxide, wherein the cerium oxide particles prepared by this method are at the nanoscale, with uniform particle size distribution, good chemical stability, excellent electrical conductivity, and low cost.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for preparing nano-cerium oxide includes the following steps:

[0006] Step S1: Place BaCeO3 or CaCeO3 powder in a heating furnace;

[0007] Step S2: After purging the heating furnace with inert gas, introduce carbon dioxide into the heating furnace, then raise the temperature to 500-1000℃ and continue the reaction for 6-12 hours, then cool to room temperature;

[0008] Step S3: Remove the BaCO3 generated in the reaction with acid and allow the carbon dioxide to completely evaporate. After filtration and drying, nano CeO2 is obtained.

[0009] Preferably, in step S1, the heating furnace is a large box furnace or tube furnace. The tube furnace has a diameter of 30cm and a length of 1.5m. 15-25 grams of BaCeO3 powder is placed in the corundum boat, which is located in the constant temperature zone in the middle of the tube furnace.

[0010] Preferably, the acid is hydrochloric acid or sulfuric acid, with a concentration of 0.3-0.6 mol / L.

[0011] Preferably, in step S2, the tube furnace is first purged with helium for 15 minutes before the carbon dioxide is introduced.

[0012] Two other objectives of this invention are to provide nano-cerium oxide prepared by the above method and its application in fuel cells, sensors or catalysts.

[0013] The beneficial effect of this invention is that by capturing CO2 at low temperature with barium cerate to replace cerium dioxide, the cerium dioxide remains at the nanoscale and does not agglomerate due to the low temperature, and the prepared product maintains chemical stability at high temperature, which greatly improves the conductivity of the material. Attached Figure Description

[0014] Figure 1 This is the XRD pattern of nano-cerium oxide from Example 1;

[0015] Figure 2 This is a SEM image of nano-cerium oxide from Example 1;

[0016] Figure 3 This is the particle size distribution of nano-cerium oxide in Example 1;

[0017] Figure 4 The electrical conductivity of nano-cerium oxide in Example 1;

[0018] Figure 5 This is the XRD pattern of nano-cerium oxide in Example 2;

[0019] Figure 6 This is the electrical conductivity of nano-cerium oxide in Example 2. Detailed Implementation

[0020] The present invention will be further described below through specific embodiments: Example 1

[0021] Step S1: Weigh 20g of BaCeO3 powder, place the powder in a corundum boat, and then place it in the constant temperature zone in the middle of a tube furnace with a diameter of 30cm and a length of 1.5m.

[0022] Step S2: First, purge the reactor with helium for 15 minutes, then introduce CO2 and heat to 600°C at a rate of 3°C / min. When the set temperature is reached, continue the reaction for 8 hours at a gas flow rate of 300 sccm. After the isothermal reaction is complete, continue introducing CO2 and cool to room temperature.

[0023] Step S3: Wash the powder obtained in step S2 with excess 0.5 mol / L dilute hydrochloric acid, add excess acid to ensure that all CO2 evaporates, BaCl2 is eluted by hydrochloric acid, filter the precipitate to obtain nano CeO2.

[0024] The obtained powder samples were characterized using XRD and SEM, and the results are as follows: Figure 1 and Figure 2 As shown.

[0025] Depend on Figure 1 and Figure 2 As can be seen, the CeO2 sample morphology consists of spherical or cubic particles with uniform distribution and no agglomeration. Only a very small number of particles aggregate due to intermolecular forces. The particle size distribution histogram obtained from the analysis is shown below. Figure 3 As shown. By Figure 3 The maximum particle size peak can be observed, corresponding to a particle size mainly distributed in the range of 30~120 nm, with the main particle size being 50 nm. Compared with CeO2 prepared by high-temperature solid-state method, this more stable nanomaterial can be used in high-temperature material applications, including SOFCs, catalysis, and solid gas sensors, thus solving the problem of the stability of nanoparticles at high temperatures for extended periods.

[0026] The electrical conductivity of the nano-cerium oxide prepared in this embodiment is as follows: Figure 4 As shown in Figure 4, the conductivity of the material was determined using an electrochemical workstation (ZAHNER) in an air atmosphere. Before each electrical measurement, the sample was equilibrated at a constant temperature for 0.5 hours, followed by two measurements involving heating and cooling. The conductivity results are shown in Figure 4.

[0027] Depend on Figure 4 It is evident that the nano-oxide prepared by this invention has excellent electrical conductivity. The preparation temperature of commercially available cerium oxide is generally around 1300℃. Compared with commercially available cerium oxide, the conductivity of this invention is almost an order of magnitude higher, while the activation energy is lower. It can be used in fuel cells, sensors, and many other applications. Example 2

[0028] Step S1: Weigh 15g of CaCeO3 powder, place the powder in a corundum boat, and then place it in the constant temperature zone in the middle of a tubular furnace with a diameter of 30cm and a length of 1.5m.

[0029] Step S2: First, purge the reactor with helium for 15 minutes, then introduce CO2 and heat to 600°C at a rate of 3°C / min. When the set temperature is reached, continue the reaction for 12 hours at a gas flow rate of 300 sccm. After the isothermal reaction is complete, continue introducing CO2 and cool to room temperature.

[0030] Step S3: Wash the powder obtained in step S2 with excess 0.3 mol / L dilute sulfuric acid, add excess acid to ensure that all CO2 evaporates, CaCl2 is eluted by hydrochloric acid, filter the precipitate to obtain nano CeO2.

[0031] In this embodiment, Ba is replaced with Ca, which also has carbon capture properties. Figure 5The XRD pattern for CeO2 preparation shows the absence of other impurity peaks, indicating high purity of all products. Compared with commercially available products, the peaks are sharper, indicating better crystallinity.

[0032] Figure 6 Regarding electrical conductivity, the ionic conductivity of CeO2 is greatly affected by temperature. At lower synthesis temperatures, the grain contact between CeO2 grains and grain boundaries is strengthened, and a "bridging" structure is formed between the grains, which accelerates mass transfer. As can be seen from the figure, the conductivity of the nano-oxide prepared by this invention is significantly improved compared with commercially available products, thus improving electrical performance. Example 3

[0033] Step S1: Weigh 25-28g of BaZnO2 powder, place the powder in a corundum boat, and then place it in the constant temperature zone in the middle of a tubular furnace with a diameter of 30cm and a length of 1.5m.

[0034] Step S2: First, purge the reactor with helium for 15 minutes, then introduce CO2 and heat to 600°C at a rate of 3°C / min. When the set temperature is reached, continue the reaction for 6 hours at a gas flow rate of 300 sccm. After the isothermal reaction is complete, continue introducing CO2 and cool to room temperature.

[0035] Step S3: Wash the powder obtained in step S2 with excess 0.6 mol / L dilute hydrochloric acid, add excess acid to ensure that all CO2 evaporates, BaCl2 is eluted by hydrochloric acid, filter the precipitate to obtain nano ZnO.

[0036] The obtained powder sample was characterized by XRD, and the results showed that zinc oxide particles were successfully prepared. By utilizing the principle of capturing CO2 at lower temperatures to replace oxides, various oxides can be prepared. This embodiment provides a novel method for preparing zinc oxide.

[0037] The above embodiments are merely illustrative of the concept and implementation of the present invention and are not intended to limit it. Under the concept of the present invention, technical solutions without substantial changes are still within the scope of protection.

Claims

1. A method for preparing nano-cerium oxide, characterized in that... Includes the following steps: Step S1: Place BaCeO3 or CaCeO3 powder in a heating furnace; Step S2: After purging the heating furnace with inert gas, introduce carbon dioxide into the heating furnace, then raise the temperature to 500-600℃ and continue the reaction for 6-12 hours, then cool to room temperature; Step S3: Remove the BaCO3 or CaCO3 generated in the reaction with acid and completely volatilize the carbon dioxide. After filtration and drying, nano CeO2 is obtained.

2. The method for preparing nano-cerium oxide as described in claim 1, characterized in that: In step S1, the heating furnace is a large box furnace or tube furnace. The tube furnace has a diameter of 30cm and a length of 1.5m. 15-25 grams of BaCeO3 or CaCeO3 powder is placed in the corundum boat, which is located in the constant temperature zone in the middle of the tube furnace.

3. The method for preparing nano-cerium oxide as described in claim 1, characterized in that: The acid is hydrochloric acid or sulfuric acid, with a concentration of 0.3-0.6 mol / L.

4. The method for preparing nano-cerium oxide as described in claim 1, characterized in that: In step S2, the tube furnace is first purged with helium for 15 minutes before the carbon dioxide is introduced.

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