Black cerium dioxide nano material with high stability and rich oxygen defects and preparation method thereof

Abstract

The invention belongs to the related technical field of preparation of cerium dioxide nano materials, and particularly relates to a high-stability oxygen-defect-enriched black cerium dioxide nano material and a preparation method thereof.The preparation method comprises the steps that cerium acetate powder serves as a raw material and is added into a feeder of plasma reaction equipment, and the oxygen-defect-enriched black cerium dioxide nano material is obtained by regulating and controlling parameters of the radio-frequency low-temperature thermal plasma reaction equipment; the oxygen deficiency concentration of the black cerium dioxide is higher than that of common cerium dioxide, the absorption intensity of the black cerium dioxide in a visible light region is higher than that of the black cerium dioxide in an ultraviolet light region, and the black cerium dioxide has the characteristic of long-term stability in air below 200 DEG C. The black cerium dioxide nano material is quick in preparation process, simple in raw materials, easy to regulate and control parameters of thermal plasma reaction equipment, and suitable for large-scale production. The obtained high-stability black cerium dioxide can stably exist in air for a long time and has strong light absorption performance in an ultraviolet-visible-infrared light area, and the light absorption performance is superior to that of a common cerium dioxide material. The electronic structure and the surface chemical property of the cerium dioxide material are changed through oxygen enrichment defects, so that the photocatalytic performance, the adsorption performance, the electrocatalytic activity and the like of the cerium dioxide material are enhanced, and the cerium dioxide material has a wider application prospect due to improvement of the performances.

Description

Technical Field

[0001] The invention belongs to the technical field related to the preparation of cerium dioxide nanomaterials, and specifically relates to a black cerium dioxide nanomaterial with high stability and rich oxygen defects and a preparation method thereof. Background Art

[0002] Rare earth compounds with unique optical, electrical and magnetic properties are an important class of inorganic materials. Cerium dioxide (CeO2) is one of the most widely used rare earth metal oxides, which is usually a yellow-white solid powder. As a wide-gap n-type semiconductor material, cerium dioxide can absorb ultraviolet light and part of visible light to participate in photocatalytic reactions. Therefore, it is widely used in the fields of pollutant photodegradation, photothermal catalysis, photoelectrochemical cells, etc. In general, cerium dioxide is a very important chemical material with broad application prospects in various fields, and its chemical properties can be optimized and improved through structural design and surface modification.

[0003] Introducing oxygen defects into ceria can significantly improve its many chemical properties. On the one hand, oxygen defects can increase the reactive sites of ceria, improve its charge transfer ability, and thus enhance the catalytic activity; secondly, when ceria is used as a catalyst carrier, the oxygen defects present in it can play the role of anchoring the active components of the catalyst and improve the stability of the catalyst; in addition, oxygen defects can also affect the adsorption and dissociation of gas molecules on the surface of ceria, thereby regulating the corresponding catalytic reaction mechanism, kinetics and reaction process. Oxygen defects are also an important reason for the blackening of ceria, and blackened ceria will have a wider wavelength of light absorption and better photocatalytic performance.

[0004] Compared with ordinary cerium dioxide, black cerium dioxide is a nanomaterial with special photochemical properties, which can be used in photothermal catalysis, photoelectrocatalysis, environmental pollution control and other fields. The performance advantages of black cerium dioxide mainly come from the oxygen defects and lattice defects therein. However, the traditional high-temperature reduction method has a complicated preparation process and high energy consumption cost. The prepared black cerium dioxide has a low oxygen defect concentration and cannot exist stably in the air for a long time, which is not conducive to large-scale production and practical application. Therefore, it is of practical significance to develop a method for preparing black cerium dioxide with a simple preparation process, high stability and rich oxygen defects.

[0005] Thermal plasma technology is a unique method for synthesizing nanomaterials. Its advantages are mainly reflected in three aspects: first, the high-energy processing environment can promote the dissociation and reaction between atoms and molecules, thereby effectively obtaining highly dispersed nanoparticles. Second, the rapid quenching process in the plasma flame zone (10 5 -10 6K / s) can promote the synthesis of defect-rich nanomaterials. Third, quenching under ultra-high temperature conditions can promote the passivation of the surface of nanoparticles, thereby greatly improving the stability of the material. With its advantages of high efficiency, simplicity and flexibility, thermal plasma technology can be used to prepare new materials with physical and chemical properties different from other synthesis methods. Summary of the invention

[0006] The purpose of the present invention is to develop a simple and efficient method for preparing a black cerium dioxide nanomaterial with high stability and rich oxygen defects based on the above technical analysis.

[0007] The preparation method of the high-stability, oxygen-defect-rich black cerium dioxide nanomaterial of the present invention comprises the following steps:

[0008] (1) Cerium acetate is ground, dried and sieved, and added into the feeder of the plasma equipment as a raw material.

[0009] (2) The parameters of the radio frequency low-temperature thermal plasma equipment are adjusted as follows: the middle gas and side gas use high-purity inert gas (Ar or He), and the middle gas flow rate is controlled in the range of 0.1-2.0 m 3 / h, the air velocity control range is 1.0-10.0 m 3 / h; the carrier gas used is H2 / Ar mixed gas (Ar ratio range is 0-100%), and the carrier gas flow rate control range is 0.1-1.0 m 3 / h; feed rate is 0.1-20.0 g / min; instrument power is 15-25kW.

[0010] (3) A black cerium dioxide product with high stability and rich oxygen defects is collected from the receiving box of the plasma equipment.

[0011] The present invention provides a method for preparing a black cerium dioxide nanomaterial with high stability and rich oxygen defects. The material prepared by the method is a pure black fluffy powder with a particle size of about 15 nm. The material has a strong light absorption performance in the ultraviolet-visible-infrared light region that is significantly better than that of ordinary cerium dioxide. The absorption intensity in the visible-near infrared light region is greater than that in the ultraviolet light region. At the same time, the oxygen vacancy content of the cerium dioxide is 8.9 times that of ordinary cerium dioxide, which is 5.77*10 21 / cm 3 It has stable physical and chemical properties below 200°C and is difficult to be oxidized by air.

[0012] The technical solution in the present invention has at least the following technical effects or advantages:

[0013] (1) The raw materials are simple, the parameters of the thermal plasma equipment can be adjusted according to requirements, and it is easy to mass produce.

[0014] (2) The preparation process is simple and quick.

[0015] (3) The obtained high-stability, oxygen-defect-rich black cerium dioxide nanomaterial has an oxygen vacancy content significantly higher than that of ordinary cerium dioxide, and is stable for a long time in air below 200°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a photograph of the high stability, oxygen defect-rich black cerium dioxide nanomaterial of the present invention.

[0017] Figure 2 It is an X-ray diffraction spectrum of the black cerium dioxide nanomaterial with high stability and rich oxygen defects of the present invention.

[0018] Figure 3 This is a transmission electron microscope photograph of the high-stability, oxygen-defect-rich black cerium dioxide nanomaterial of the present invention.

[0019] Figure 4 It is the ultraviolet-visible-near infrared absorption spectrum of the black cerium dioxide nanomaterial with high stability and rich oxygen defects of the present invention.

[0020] Figure 5 It is the infrared absorption spectrum of the black cerium dioxide nanomaterial with high stability and rich oxygen defects of the present invention.

[0021] Figure 6 It is the electron paramagnetic resonance spectrum of the black cerium dioxide nanomaterial with high stability and rich oxygen defects of the present invention.

[0022] Figure 7 The electronic paramagnetic resonance spectrum and color photograph of the sample of the black cerium dioxide nanomaterial with high stability and rich oxygen defects treated in an air atmosphere at 200° C. of the present invention.

[0023] The following will be described in detail with reference to the embodiments and experimental data for the high stability, oxygen-defect-rich black cerium dioxide nanomaterial and its preparation method of the present application. In this specification, the use of terms shall conform to the usual meaning in the art unless otherwise specified. If there is a conflict in the interpretation of terms, this specification shall prevail.

[0024] The various raw materials, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods, unless otherwise specified.

[0025] Example 1

[0026] Weigh 50 g of cerium acetate, grind it and dry it in an oven at 80°C for 24 hours. After cooling to room temperature, pass it through a 60-mesh sieve and put it into the feed bin of the thermal plasma equipment.

[0027] The control parameters of the thermal plasma reaction equipment are as follows: the gases used for the middle gas and the side gas are high-purity argon, and the flow rate of the middle gas is controlled to 0.5 m 3 / h, the side air flow is controlled at 4.5 m 3 / h; the carrier gas used is high-purity argon, and the carrier gas flow rate is controlled at 0.2m 3 / h; the feed rate is 5.0 g / min, and the instrument power is controlled at 20 kW. After 10 minutes of thermal plasma treatment, black cerium dioxide nanomaterials with high stability and rich oxygen defects can be obtained in the receiving box.

[0028] Example 2

[0029] The instrument power was adjusted to 25 kW, and other conditions were the same as in Example 1.

[0030] Example 3

[0031] The carrier gas was replaced with a H2 / Ar mixed gas (H2: 10%, Ar: 90%), and other conditions were the same as in Example 1.

[0032] Experimental results and test analysis:

[0033] Attached Figure 1 The sample placed on the weighing paper is a black cerium dioxide nanomaterial with high stability and rich oxygen defects. It can be seen from the figure that the material prepared by the present invention is a black fluffy powder.

[0034] Attached Figure 2 This is an X-ray diffraction spectrum of a black cerium dioxide nanomaterial with high stability and rich oxygen defects. Compared with the standard card of cerium dioxide (PDF#01-081-0792), the black fluffy powder prepared by the present invention is cerium dioxide. The particle size is calculated by the Scherrer formula, and the result is 15.8 nm.

[0035] Attached Figure 3 This is a transmission electron microscope photograph of a black cerium dioxide nanomaterial with high stability and rich oxygen defects. It can be seen from the photograph that the particle size of the black cerium dioxide nanomaterial is 10 to 20 nm.

[0036] Attached Figure 4 , Figure 5 They are the UV-visible-near-infrared absorption spectrum and infrared absorption spectrum of black cerium dioxide nanomaterials with high stability and oxygen defects. Compared with ordinary cerium dioxide prepared by conventional methods, the absorption intensity of black cerium dioxide in the visible-near-infrared light region is greater than that in the ultraviolet light region, and it has strong light absorption properties in the UV-visible-infrared light region that are significantly better than ordinary cerium dioxide.

[0037] Attached Figure 6This is the electron paramagnetic resonance spectrum of a black cerium dioxide nanomaterial with high stability and rich oxygen defects. The test results show that black cerium dioxide has a response peak at g=2.003 (for materials with oxygen vacancies, a peak usually appears at a g value of 2.003). In contrast, ordinary cerium dioxide has no peak at the corresponding position, which proves that the black cerium dioxide nanomaterial prepared by the present invention has a rich oxygen vacancy content.

[0038] Attached Figure 7 The present invention provides an electron paramagnetic resonance spectrum and a color photograph of a black cerium dioxide nanomaterial with high stability and rich oxygen defects after treatment at 200°C in an air atmosphere. The results show that the oxygen vacancy content and the color of the black cerium dioxide nanomaterial after treatment have not changed significantly compared with those before treatment, proving that the oxygen vacancies in the black cerium dioxide nanomaterial prepared by the present invention have stable physicochemical properties below 200°C and are difficult to be oxidized by air.

[0039] Finally, it should be noted that the above-described embodiments are only intended to better illustrate the technical solution of the present invention, and are not intended to limit the scope of protection of the present invention. In the opinion of a person skilled in the art, the technical solution of the present invention can still be appropriately modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also includes these modifications and variations.

Claims

1. A black cerium dioxide nanomaterial with high stability and rich oxygen defects and a preparation method thereof, characterized in that: Highly stable, oxygen-defect-rich black cerium dioxide is prepared in one step through radio frequency low-temperature thermal plasma reaction equipment.

2. The method for preparing a black cerium dioxide nanomaterial with high stability and rich oxygen defects according to claim 1, characterized in that The plasma used is radio frequency low-temperature thermal plasma.

3. The method for preparing a black cerium dioxide nanomaterial with high stability and rich oxygen defects according to claim 1, characterized in that The middle gas and side gas used in the radio frequency low-temperature thermal plasma reaction equipment include at least one of the following: high-purity Ar and high-purity He inert gases.

4. The method for preparing a black cerium dioxide nanomaterial with high stability and rich oxygen defects according to claim 2, characterized in that The gas flow rate control range of the radio frequency low temperature thermal plasma reaction equipment is 0.1-2.0 m 3 / h, the air velocity control range is 1.0-10.0 m 3 / h.

5. The method for preparing a black cerium dioxide nanomaterial with high stability and rich oxygen defects according to claim 1, characterized in that The carrier gas used in the radio frequency low-temperature thermal plasma reaction equipment is a H2 / Ar mixed gas (the proportion of Ar ranges from 0-100%).

6. The method for preparing a high-stability, oxygen-defect-rich black cerium dioxide nanomaterial according to claim 5, characterized in that The carrier gas flow rate control range of the radio frequency low temperature thermal plasma reaction equipment is 0.1-1.0 m 3 / h.

7. The method for preparing a high-stability, oxygen-defect-rich black cerium dioxide nanomaterial according to claim 1, characterized in that The feed rate of the radio frequency low-temperature thermal plasma reaction equipment is 0.1-20.0 g / min.

8. The method for preparing a black cerium dioxide nanomaterial with high stability and rich oxygen defects according to claim 1, characterized in that The instrument power of the radio frequency low temperature thermal plasma reaction equipment is 15-25 kW.

9. The black cerium dioxide nanomaterial with high stability and rich oxygen defects according to claim 1, characterized in that: The black cerium dioxide material is prepared by the preparation method of the high-stability, oxygen-defect-rich black cerium dioxide material according to any one of claims 1 to 8.

10. The black cerium dioxide nanomaterial with high stability and rich oxygen defects according to claim 1, characterized in that: The black cerium dioxide nanoparticles are fluffy pure black and have an oxygen defect concentration greater than 5.77*10 21 / cm 3 Its absorption intensity in the visible-near infrared region is greater than that in the ultraviolet region, and it is stable for a long time in air below 200°C.

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