Nanocrystalline magnetic ferrihydrite material, preparation method and application thereof

Abstract

The application provides a nanocrystalline magnetic hydroxyl ferric oxide material and a preparation method and application thereof, and belongs to the field of material preparation. A platinum net is used as a cathode, a carbon rod is used as a counter electrode, Ag / AgCl is used as a reference electrode, and FeCl3 aqueous solution is used as an electrolyte. After voltage is applied by a constant voltage discharge device for electrolysis, flocculent substances can be obtained, and hydrogen gas is generated. Then, the precipitated substances are collected after washing and suction filtration, and the precipitated substances are dried and ground to obtain a hydroxyl ferric oxide material with a spinel crystal structure. The hydroxyl ferric oxide material is a nanoparticle with a particle size of 5-100 nm, has magnetism, and the saturation magnetization value can reach 47.8emu / g. The hydroxyl ferric oxide material is used as a negative electrode material and is applied to a lithium ion button cell. The synthesis method is novel, the preparation process is simple, the reaction condition is mild, the operation is safe, the energy consumption in the reaction process is low, and the method is easy to scale up. The synthesized hydroxyl ferric oxide has the characteristics of high product quality, few impurities and good dispersity.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, and particularly relates to a nanocrystalline magnetic iron hydroxyl oxide material, its preparation method, and its application. Background Technology

[0002] Iron hydroxyl oxide (FeOOH) exists in various crystal forms, typically as polymorphs of goethite (α-FeOOH), lepidocrocite (β-FeOOH), tetragonal lepidocrocite (γ-FeOOH), and hexagonal lepidocrocite (δ-FeOOH). Among these common crystal forms, only δ-FeOOH is magnetic, and therefore it is used in bioimaging technology to improve the accuracy and clarity of images. Magnetic nanoparticles prepared using δ-FeOOH can also be precisely targeted to target cells or tissues in the human body, thus playing an important role in biomedical fields such as biolabeling and bioseparation.

[0003] In addition to these common iron hydroxyl oxide crystal forms, Morán et al. first synthesized a novel magnetic iron hydroxyl oxide with a spinel crystal structure in 2002 [Inorg. Chem. 2002, 41, 5961-5967]: First, sodium oxide and hematite raw materials were reacted at 400-500℃ for 24 h to synthesize an α-NaFeO2 precursor. This precursor material was then reacted in molten ammonium nitrate medium (200℃) for 48 h to achieve H… + To Na + The substitution yields a spinel-structured magnetic iron hydroxyl oxide material. However, this preparation process has three main drawbacks: (1) long reaction time under high temperature conditions, high energy consumption, and safety concerns; (2) the ammonium nitrate used is an oxidant, which is prone to explosive decomposition upon heating and releases NH3, posing safety and environmental hazards; (3) the reaction steps are cumbersome and lengthy, making it difficult to control product quality and hindering large-scale industrial production. In addition, patent [CN103977800B] discloses a method for synthesizing nano-magnetic iron hydroxyl oxide with a core-shell structure that has a large specific surface area, good magnetic properties, easy separation, and high catalytic activity; patent [CN117229820B] prepared a magnetic iron hydroxyl oxide material with an amorphous structure. However, both of these patents involve the use of corrosive alkaline solvents in the synthesis process and have problems such as long reaction time, which are not conducive to scale-up synthesis. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings mentioned in the background art by proposing a method for preparing magnetic iron hydroxyl oxide that features mild reaction conditions, simple preparation process, safe operation, environmental friendliness, high product quality, low energy consumption, and easy scale-up synthesis. At the same time, the application of the prepared iron hydroxyl oxide is explored.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] A method for preparing a nanocrystalline magnetic iron hydroxyl oxide material includes the following steps:

[0007] Step (1): Using a platinum mesh as the cathode, a carbon rod as the counter electrode, Ag / AgCl as the reference electrode, and FeCl3 aqueous solution as the electrolyte, a DC voltage of a certain value is applied through a constant voltage discharge device. After electrolysis for a certain period of time, flocculent material is obtained and hydrogen gas is generated.

[0008] Step (2): Wash the flocculent material with deionized water, filter it, and collect the precipitate.

[0009] Step (3): Dry the precipitate obtained by vacuum filtration;

[0010] Step (4): Grind the dried precipitate to obtain iron hydroxyl oxide powder.

[0011] Furthermore, in step (1), the voltage range of the constant voltage discharge device is 0.4-0.8V, and the discharge time is 5-120min;

[0012] Furthermore, in step (3), the drying temperature is 60-120℃ and the drying time is 60-240min;

[0013] Furthermore, in step (1), the concentration of the FeCl3 aqueous solution is 0.1-3 mol / L;

[0014] A nanocrystalline magnetic iron hydroxyl oxide material is prepared using the method described above. This nanocrystalline magnetic iron hydroxyl oxide material consists of nanoparticles with a particle size of 5-100 nm; it is magnetic and has a spinel structure. The saturation magnetization of this nanocrystalline magnetic iron hydroxyl oxide material can reach over 45 emu / g, with a maximum value reaching 47.8 emu / g.

[0015] An application of a nanocrystalline magnetic iron hydroxyl oxide material: This nanocrystalline magnetic iron hydroxyl oxide material is used as a negative electrode material in lithium-ion button batteries, achieving a first-cycle discharge specific capacity of 808 mAh g⁻¹. -1 .

[0016] The basic reaction process of this invention is as follows:

[0017] First, after the applied current is passed in step (1), the water molecules in the electrolyte first gain electrons at the cathode and are reduced to free OH-. - And hydrogen gas. Secondly, free Fe in the electrolyte. 3+ It will react with the free OH generated at the cathode -The reaction combines to form ferric hydroxide (Fe(OH)3) precipitate. After drying and dehydration, the Fe(OH)3 precipitate yields ferric hydroxide (FeOOH).

[0018] The basic reaction equations involved in the reaction process are as follows:

[0019] 6H2O+6e - →6OH - +3H2 (1)

[0020] 2Fe 3+ +6OH - →2Fe(OH)3 (2)

[0021] 2Fe(OH)3-2H2O→2FeOOH (3)

[0022] Overall reaction: 2Fe³⁺ + 6e⁻ - +4H₂O→2FeOOH+3H₂

[0023] In summary, the innovation of this invention lies in the fact that magnetic iron hydroxyl oxide nanocrystals with a spinel structure can be obtained under mild reaction conditions without the need for additional precipitants or structure-directing agents. Furthermore, the sample preparation process does not consume electrode materials, thus saving energy and facilitating large-scale continuous production. In addition, the additional green hydrogen produced enhances the added value of this preparation process.

[0024] The advantages of this invention compared to the prior art are:

[0025] (1) The synthesis process is simple, the conditions are mild, the operation is convenient, the process is controllable, energy-saving and pollution-free, and it is suitable for large-scale production.

[0026] (2) The obtained nanocrystalline iron hydroxyl oxide has stronger magnetism: at room temperature, its saturation magnetization is as high as 47.8 emu / g, which is much higher than that of δ-FeOOH [Chem.Sci.,2014,5,2251]. In addition, the obtained nanocrystalline iron hydroxyl oxide product also has the advantages of high purity, few impurities, good dispersibility, and easy separation.

[0027] (3) In step (1) of this invention, while generating nanocrystalline iron hydroxyl oxide, a green hydrogen production method is also provided. The generated hydrogen has broad application prospects in industries such as hydrogen fuel cell vehicles, power generation, chemical industry, and metallurgy. Attached Figure Description

[0028] Figure 1 The image shows the XRD pattern of the precipitate after filtration in Example 1.

[0029] Figure 2The image shows the FTIR spectrum of the precipitate after filtration in Example 1.

[0030] Figure 3 The image shows the XRD pattern of the iron hydroxyoxide prepared in Example 1.

[0031] Figure 4 The image shows the FTIR spectrum of the iron hydroxyoxide prepared in Example 1.

[0032] Figure 5 This is the magnetization curve of the iron hydroxyoxide prepared in Example 1.

[0033] Figure 6 This is a SEM image of the iron hydroxyoxide prepared in Example 1.

[0034] Figure 7 This is a TEM image of the iron hydroxyoxide prepared in Example 1.

[0035] Figure 8 The image shown is an HRTEM image of the iron hydroxyoxide prepared in Example 1.

[0036] Figure 9 The first cycle charge-discharge curve of the lithium-ion battery with iron hydroxyl oxide prepared in Application Example 1 is shown. Detailed Implementation

[0037] The present invention will be further described below with reference to specific implementation examples. Example 1

[0038] 200 mL of FeCl3 with a molar concentration of 2 mol / L was injected into a 250 mL electrolytic cell. A 2.5 cm × 2.5 cm platinum mesh was used as the cathode, and a Φ2 × 15 cm carbon rod was used as the counter electrode. The cell was connected to an electrochemical workstation, and a constant voltage discharge was set with an output voltage of 0.4 V for 30 min. During the electrolysis process, flocculent substances were continuously and slowly precipitated. After electrolysis, the turbid liquid was filtered with deionized water using 5 µm aqueous filter paper. After filtration, the liquid was placed in a forced-air drying oven at 120 °C for 60 min to obtain a black powder.

[0039] X-ray diffraction (XRD) characterization of the filtered precipitate showed that... Figure 1 The product is amorphous and is Fe. 3+ The amorphous ferric hydroxide colloidal precipitate formed by hydrolysis [Environ. Sci. Technol. 2007, 41, 6117–6123]; Fourier transform infrared spectroscopy (FTIR) analysis was performed on the precipitate after filtration. Figure 2 A very clear signal of OH bond vibration was observed (1630 cm⁻¹). -1 and 3435cm-1 (peak at) and Fe 3+ -OH - OH in action - Vibration signal (1048cm) -1 The peak at the precipitate further confirmed that the precipitate contained a large number of -OH groups; XRD characterization of the final product showed that ( Figure 3 The powder is iron hydroxide with a spinel structure. FTIR analysis was performed on the final product (…). Figure 4 A relatively strong OH bond vibration signal (1628 cm⁻¹) was still observed. -1 and 3438cm -1 (peak at the location), but Fe 3+ -OH - OH in action - Vibration signal (1047cm) -1 The peak at 579 cm⁻¹ is very weak, while the vibrational signal of the Fe-O bond is very strong (579 cm⁻¹). -1 The peak at the specified location is consistent with the structural characteristics of iron hydroxyl oxide. Furthermore, magnetic testing of iron hydroxyl oxide reveals a coercivity (Hc) of only 30.97 Oe and a saturation magnetization of 47.8 emu / g, indicating that it is a soft magnetic material. Figure 5 ). Figure 6 The image shows the scanning electron microscope (SEM) characterization of iron hydroxyoxide, which reveals a coral-like morphology composed of stacked powder particles. Figure 7 Transmission electron microscopy (TEM) and Figure 8 High-resolution transmission electron microscopy (HRTEM) characterization showed that the powder particles have a nanocrystalline structure with a particle size of 8-80 nm. Example 2

[0040] 200 mL of FeCl3 with a molar concentration of 0.1 mol / L was injected into a 250 mL electrolytic cell. A 2.5 cm × 2.5 cm platinum mesh was used as the cathode, and a Φ2 × 8 cm carbon rod was used as the counter electrode. The cell was connected to an electrochemical workstation, and a constant voltage discharge was set with an output voltage of 0.8 V and a discharge time of 5 min. During the electrolysis process, flocculent substances were continuously and slowly precipitated. After electrolysis, the turbid liquid was filtered with deionized water using 5 µm aqueous filter paper. After filtration, the liquid was placed in a forced-air drying oven at 60 °C for 240 min to obtain a black powder.

[0041] XRD results showed that the powder particles were spinel-structured iron hydroxyl oxide. TEM characterization showed that the particle size ranged from 10 to 70 nm. SEM showed that the morphology of the prepared iron hydroxyl oxide was similar to that of the iron hydroxyl oxide prepared in Example 1. Magnetic detection results showed that the coercivity (Hc) of the iron hydroxyl oxide was 31.86 Oe and the saturation magnetization was 45.4 emu / g, indicating that it is a soft magnetic material. Example 3

[0042] 200 mL of FeCl3 with a molar concentration of 3 mol / L was injected into a 250 mL electrolysis cell. A 2.5 cm × 2.5 cm platinum mesh was used as the cathode, and a Φ4 × 10 cm carbon rod was used as the counter electrode. The cell was connected to an electrochemical workstation, and a constant voltage discharge was set with an output voltage of 0.7 V for 120 min. During the electrolysis process, flocculent material continuously formed and then slowly precipitated. After electrolysis, the turbid liquid was filtered with deionized water using 5 µm aqueous filter paper. After filtration, the liquid was placed in a forced-air drying oven at 80 °C for 180 min to obtain a black powder. SEM characterization showed that the powder particles had a coral-like morphology of stacked particles, similar to the morphology in Examples 1 and 2. TEM characterization showed that the size distribution of the powder particles ranged from 5 to 100 nm. After magnetic testing, the coercivity (Hc) of iron hydroxyl oxide was found to be 31.15 Oe and the saturation magnetization was 46.1 emu / g, thus classifying it as a soft magnetic material.

[0043] Application Example 1

[0044] The iron hydroxyl oxide prepared in Example 1 was mixed with a conductive agent and a binder at a mass ratio of 7:2:1 and used as the working electrode, with metallic Li as the counter electrode, to assemble a lithium-ion button battery. Using a Xinwei (CT-4008Tn-5V10mA-HWX) electrical testing system, a current density of 100 mAg was achieved within a voltage range of 0.1-3.0V. -1 The charge-discharge performance of the assembled button cell was tested under the following conditions. The results showed that its first-cycle charge specific capacity was 621.5 mAh g. -1 The discharge specific capacity is 808mAhg. -1 ( Figure 9 ).

[0045] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing a nanocrystalline magnetic iron oxyhydroxide material, characterized in that, The method comprises the following steps: Step (1), using platinum net as cathode, carbon rod as counter electrode, Ag / AgCl as reference electrode, FeCl3 aqueous solution as electrolyte, applying voltage by constant voltage discharge device to obtain flocculent substance and produce hydrogen gas; Step (2), washing the flocculent substance with deionized water, and collecting precipitate after suction filtration; Step (3), drying the precipitate obtained by suction filtration; Step (4), grinding the dried precipitate to obtain nanocrystalline magnetic hydroxyl iron oxide powder with spinel crystal structure, saturation magnetization of 45-47.8 emu / g and particle size of 5-100 nm.

2. The production method according to claim 1, characterized by, In step (1), the voltage range of the constant voltage discharge device is 0.4-0.8 V, and the discharge time is 5-120 min.

3. The preparation method according to claim 1, characterized in that, In step (3), the drying temperature is 60-120 ℃, and the drying time is 60-240 min.

4. The method of claim 1, wherein, In step (1), the concentration of FeCl3 aqueous solution is 0.1-3 mol / L.

5. A nanocrystalline magnetic iron oxyhydroxide material, characterized in that, The nanocrystalline magnetic hydroxyl iron oxide material is prepared by the preparation method of any one of claims 1-4.

6. Application of the nanocrystalline magnetic hydroxyl iron oxide material of claim 5 as negative electrode material of lithium ion button cell.

7. Use according to claim 6, characterized in that, The first cycle discharge specific capacity of the lithium ion button cell reaches 808 mAhg -1 .

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