Fe-doped δ-MnO2 nanoparticles and their preparation method

Abstract

This invention belongs to the field of inorganic nanomaterial synthesis technology, and discloses a Fe-doped δ-MnO2 nanoparticle and its preparation method. The method involves uniformly mixing potassium ferrate and manganese salt, calcining at 200–600°C for a high-temperature solid-state reaction, and after the reaction is complete, washing and drying the resulting product to obtain Fe-doped δ-MnO2. This invention utilizes FeO4 in potassium ferrate. 2‑ The strong oxidizing properties of manganese salts will cause Mn to form in the manganese salt. 2+ Potassium ferrate is oxidized to MnO2, and the potassium in it... + Sufficient counter cations can be provided to the interlayer of δ-MnO2 to stabilize its layered structure. Furthermore, FeO4... 2‑ Mn 2+ Reduced to Fe 3+ Afterwards, some Fe 3+ Fe-doped δ-MnO2 nanoparticles are obtained by entering the δ-MnO2 lattice through a solid-state reaction. This preparation method is simple, controllable, and reproducible, and the raw materials are all solid powders, making it easy to achieve large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of inorganic nanomaterial synthesis, and more particularly relates to a Fe-doped δ-MnO2 nanoparticle and a preparation method thereof. BACKGROUND

[0002] MnO2 is an important basic inorganic material, and is widely used in the fields of energy, environment, medical treatment and industrial manufacturing as a manganese oxide. At present, the rapid development of nanomaterial field brings unlimited opportunities and challenges to the basic research and application of MnO2, and therefore, the synthesis and performance research of MnO2 nanomaterial has become a current research hotspot. MnO2 has multiple crystal structures, and the basic structural unit thereof is [MnO6] octahedron. According to the different linking modes (common edge or common corner) of the [MnO6] octahedron, the crystal structure of MnO2 can be divided into two categories: one-dimensional tunnel structure and two-dimensional layer structure. The crystal structure of MnO2 can be represented by (m x n), wherein m and n respectively represent the number of [MnO6] octahedrons in the vertical and horizontal unit chains. The common one-dimensional tunnel structure of MnO2 includes β-MnO2 (1 x 1), α-MnO2 (2 x 2) and γ-MnO2 (1 x 1 and 1 x 2 intergrowth).

[0003] MnO2 with a layer structure is called δ-MnO2, and the number of [MnO6] octahedrons in the horizontal unit chain in the structure thereof is n = ∞. There are three common layer MnO2, which are Vemadite with (1 x ∞) structure, Bimessite with (2 x ∞) structure and Buserite with (3 x ∞) structure. These layer MnO2 have different interlayer distances due to the occupation of different counter cations in the interlayer, and K + , NH4 + are the most common counter cations. The preparation methods of δ-MnO2 include sol-gel method, solid phase method, reflux method, hydrothermal method, low-temperature liquid phase method and ultrasonic method. At present, δ-MnO2 is usually prepared by using potassium permanganate as a manganese source and using a reducing agent (such as glucose) to oxidize and reduce the same by means of high-temperature solid phase method. However, there is little research on the preparation of δ-MnO2 by using an oxidizing agent to oxidize Mn 2+ . SUMMARY

[0004] In order to solve the above-mentioned problems and shortcomings of the prior art, the purpose of the present application is to provide a preparation method of Fe-doped δ-MnO2 nanoparticles. The method uses high-temperature solid phase method to prepare Fe-doped δ-MnO2 nanoparticles by means of oxidation reaction.

[0005] Another purpose of the present application is to provide Fe-doped δ-MnO2 nanoparticles prepared by the above-mentioned method.

[0006] The object of the present application is achieved by the following technical solutions.

[0007] A preparation method of Fe-doped δ-MnO2 nanoparticles comprises the following steps: uniformly mixing potassium ferrate and a manganese salt, calcining at 200-600 DEG C, and after the reaction is completed, washing and drying the obtained product to obtain Fe-doped δ-MnO2 nanoparticles.

[0008] Preferably, the manganese salt is manganese carbonate, manganese nitrate or manganese acetate.

[0009] Preferably, the molar ratio of the potassium ferrate to the manganese salt is 1:(1-2).

[0010] Preferably, the heating rate of the calcining is 1-10 DEG C / min, and the time of the calcining is 2-6 h.

[0011] A Fe-doped δ-MnO2 nanoparticle is prepared by the method.

[0012] Preferably, the particle size of the Fe-doped δ-MnO2 nanoparticle is 40-100 nm.

[0013] The present application utilizes the strong oxidizability of FeO4 2- in potassium ferrate to oxidize Mn 2+ in the manganese salt into MnO2, and meanwhile, K + in the potassium ferrate can provide sufficient counter cations for the interlayer of δ-MnO2 to stabilize the layered structure of the δ-MnO2. 2- After FeO4 2+ is reduced into Fe 3+ by Mn 3+ , part of the Fe 3+ will enter the crystal lattice of the δ-MnO2 through high-temperature solid-phase reaction, thereby obtaining the Fe-doped δ-MnO2 nanoparticle.

[0014] Compared with the prior art, the present application has the following beneficial effects:

[0015] 1. The method of the present application does not need to use additional Fe 3+ inorganic salt as an additive to dope Fe, and the operation is simple, convenient to control and low in cost.

[0016] 2. The preparation method provided by the present application is simple and controllable, has good repeatability, and the raw materials are all solid powders, so that the industrialized macro-preparation is easy to realize. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 X-ray diffraction pattern of the Fe-doped δ-MnO2 prepared in Example 1.

[0018] Figure 2 The image shows a scanning electron microscope (SEM) image of the Fe-doped δ-MnO2 prepared in Example 1.

[0019] Figure 3 The X-ray diffraction pattern of Mn2O3 prepared for Comparative Example 1.

[0020] Figure 4 The X-ray diffraction pattern of δ-MnO2 prepared for Comparative Example 2.

[0021] Figure 5 Scanning electron microscope image of δ-MnO2 prepared for Comparative Example 2. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0023] Example 1

[0024] 2 mmol of potassium ferrate and 3 mmol of manganese carbonate were mixed evenly and placed in a muffle furnace. The mixture was heated from room temperature to 400°C at a rate of 5°C / min for 4 hours to carry out high-temperature solid-phase calcination. After the reaction was completed, the mixture was cooled to room temperature. The resulting product was washed several times with deionized water and ethanol, and then dried in a drying oven at 80°C to obtain Fe-doped δ-MnO2 nanoparticles.

[0025] The Fe-doped δ-MnO2 nanoparticles obtained above were characterized by testing. Figure 1 The image shows the X-ray diffraction pattern of the Fe-doped δ-MnO2 prepared in Example 1. Figure 1 It can be seen that the obtained product corresponds to δ-MnO2 in JCPDF standard card #80-1098, and there are no other impurity peaks, indicating that Fe-doped δ-MnO2 with a pure phase has been synthesized. Under the oxidation of strong oxidant potassium ferrate, MnCO3 can be oxidized to Fe-doped δ-MnO2. Figure 2 Scanning electron microscope (SEM) images of Fe-doped δ-MnO2 prepared in Example 1, from... Figure 2 It can be seen that the nanoparticles have a particle size of 40–100 nm and a uniform morphology. Fe is doped into δ-MnO2, and the mass percentage of Fe in the Fe-doped δ-MnO2 is 5%. Therefore, it can be concluded that FeO4 in potassium ferrate... 2- It not only participated in the redox reaction, but also incorporated Fe into the product.

[0026] Example 2

[0027] 2 mmol of potassium ferrate and 2 mmol of manganese nitrate were mixed evenly and then placed in a muffle furnace and calcined at 200 °C for 6 h at a rate of 1 °C / min from room temperature. After the reaction was completed, the mixture was cooled to room temperature and the resulting product was washed several times with deionized water and ethanol. The product was then dried in a drying oven at 80 °C to obtain Fe-doped δ-MnO2 nanoparticles with a particle size of 50–100 nm.

[0028] Example 3

[0029] 2 mmol of potassium ferrate and 4 mmol of manganese acetate were mixed evenly and then placed in a muffle furnace and calcined at 600 °C for 2 h at a heating rate of 10 °C / min. After the reaction was completed, the mixture was cooled to room temperature and the resulting product was washed several times with deionized water and ethanol. The product was then dried in a drying oven at 80 °C to obtain Fe-doped δ-MnO2 nanoparticles with a particle size of 40–100 nm.

[0030] Comparative Example 1

[0031] 3 mmol of manganese carbonate was placed in a muffle furnace and calcined at 400 °C for 4 h at a rate of 5 °C / min from room temperature. After the reaction was completed, the mixture was cooled to room temperature. The product was washed several times with deionized water and ethanol, and then dried in a drying oven to obtain Mn2O3 nanoparticles with a particle size of 20–80 nm.

[0032] Figure 3 The X-ray diffraction pattern of Mn₂O₃ prepared for Comparative Example 1. From... Figure 3 It can be seen that the obtained product corresponds to Mn2O3 in JCPDF standard card #41-1442, and there are no other impurity peaks, indicating that pure-phase Mn2O3 was synthesized. δ-MnO2 nanoparticles cannot be obtained without the addition of potassium ferrate.

[0033] Comparative Example 2

[0034] 2 mmol of potassium permanganate and 3 mmol of manganese carbonate were mixed evenly and placed in a muffle furnace. The mixture was heated from room temperature to 400°C at a rate of 5°C / min for 4 hours to carry out high-temperature solid-phase calcination. After the reaction was completed, the mixture was cooled to room temperature. The resulting product was washed several times with deionized water and ethanol, respectively. The product was then dried in a drying oven at 80°C to obtain δ-MnO2 nanoparticles.

[0035] The δ-MnO2 nanoparticles obtained above were characterized by testing. Figure 4X-ray diffraction pattern of δ-MnO2 prepared for Comparative Example 2. From... Figure 4 It can be seen that the obtained product corresponds to δ-MnO2 in JCPDF standard card #80-1098, and there are no other impurity peaks, indicating that δ-MnO2 with a pure phase was synthesized. MnCO3 can be oxidized to δ-MnO2 under the strong oxidizing agent potassium permanganate. Figure 5 The scanning electron microscope image of δ-MnO2 prepared in Comparative Example 2 is shown below. Figure 5 It can be seen that the δ-MnO2 nanoparticles have a particle size of 200–600 nm and a uniform morphology. Under the condition of adding potassium permanganate, MnCO3 can also be oxidized to δ-MnO2, and this δ-MnO2 does not contain Fe.

[0036] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing Fe-doped δ-MnO2 nanoparticles, characterized in that, The process includes the following steps: potassium ferrate and manganese salt are mixed evenly and calcined at 200-600 °C. After the reaction is complete, the resulting product is washed and dried to obtain Fe-doped δ-MnO2 nanoparticles. The manganese salt is manganese carbonate, manganese nitrate, or manganese acetate. The molar ratio of potassium ferrate to manganese salt is 1:(1-2). The calcination heating rate is 1-10 °C / min, and the calcination time is 2-6 h.

2. A Fe-doped δ-MnO2 nanoparticle, characterized in that, The Fe-doped δ-MnO2 nanoparticles are prepared by the method described in claim 1.

3. The Fe-doped δ-MnO2 nanoparticles according to claim 2, characterized in that, The Fe-doped δ-MnO2 nanoparticles have a particle size of 40~100 nm.

Images