A method for synthesizing nanotextured twinned hematite

Abstract

This invention discloses a method for synthesizing nano-curved bicrystalline hematite. The method utilizes nanorod-shaped... β FeOOH was used as the precursor material. The pH of the solution was adjusted to 1–3 using hydrochloric acid, and a hydrothermal reaction was carried out within a temperature range of 180℃–230℃. After the reaction vessel was cooled to room temperature, the solid precipitate obtained by centrifugation was washed and dried to obtain nano-curved twinned hematite. This invention represents the first successful artificial synthesis of hematite twins in the laboratory, providing a new method for the preparation and research of hematite materials with special morphologies. The method of this invention involves no addition of other active agents, making it environmentally friendly, simple, and easy to operate, and enabling large-scale preparation.

Description

Technical Field

[0001] This invention belongs to the field of mineral material synthesis technology, specifically relating to a method for the green synthesis of hematite without additives, and particularly to a method for synthesizing nano-curved twin-crystal hematite. Background Technology

[0002] Hematite is a natural semiconductor mineral with stable chemical properties and widespread distribution on the Earth's surface. Nanostructured hematite minerals are stable and possess high catalytic activity, making them environmentally friendly photoactive materials with broad application prospects in photovoltaics, catalysis, solar energy, sensors, and environmental adsorbents.

[0003] As is well known, particle shape, size, specific surface area, and microstructure determine the chemical and physical properties of nanomaterials. The type of hematite crystal facets has a great influence on its physicochemical properties. Currently, methods for synthesizing hematite with flat specific crystal faces are relatively common, such as the synthesis of nanocubes with exposed (104) crystal faces (application number: 200610156050.4); and the synthesis of trigonal eccentric tetragonal twins with two exposed crystal faces (application number: 202011471573.4). The interaction of different crystal faces of hematite can improve its catalytic activity. Therefore, there is some interest in the synthesis of hematite with multiple exposed crystal faces, such as the synthesis of nanoporous hematite with high catalytic performance (application number: 202111050200.4); the synthesis of porous hematite nanoarrays (application number: 201810488271.4); and the production of hematite pellets (application number: 200410035715.7). Therefore, understanding the synthesis conditions for controlling particle size, morphology, and crystal facets can lead to new synthesis methods, allowing for the customization of nano-hematite to achieve optimal performance. Currently, there are no reports of synthesizing nano-curved bicrystalline hematite with multiple exposed active surfaces without the addition of any surfactants. Summary of the Invention

[0004] To address the shortcomings of existing synthesis methods, the present invention aims to provide a green synthesis method for nano-curved twinned hematite without the addition of excessive surfactants. This solves the problem that existing technologies do not synthesize nano-curved twinned hematite. The present invention can further enrich the synthesis methods of hematite, and at the same time, it does not require the addition of organic solvents, surfactants and other substances, thus achieving a green and environmentally friendly synthesis of hematite in an aquatic environment with a simple process.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for synthesizing nano-curved bicrystalline hematite includes the following steps:

[0007] Step 1: Under continuous stirring, FeCl3·6H2O was dissolved in deionized water to obtain a ferric chloride solution. The ferric chloride solution was placed in a reaction flask and placed in an oven for reaction. The resulting precipitate was washed with deionized water and dried to obtain nanorod-shaped particles. β -FeOOH.

[0008] Step 2, the nanorod-shaped materials from Step 1... β -FeOOH is fully dispersed in deionized water, and the pH of the solution is adjusted by hydrochloric acid. Then, it is added to a reaction vessel and placed in an oven for hydrothermal reaction. After the reaction vessel is cooled to room temperature, the generated solid material is washed with deionized water and dried to obtain hematite nano-curved twin crystals.

[0009] Furthermore, the ferric chloride solution in step 1 is obtained by dissolving FeCl3·6H2O in deionized water, and the concentration of the ferric chloride solution is 0.03–0.8 mol / L.

[0010] Furthermore, the reaction flask in step 1 is a sealable glass flask.

[0011] Furthermore, the oven reaction temperature in step 1 is 65℃~85℃, and the reaction time is 5~9 days. If the temperature is below 65℃, complete formation will not be achieved. β -FeOOH; at temperatures above 85℃, hematite phase will appear. If the reaction time is less than 5 days, the FeCl3 hydrolysis reaction will be incomplete; if it exceeds 9 days, [the following will occur]. β -FeOOH will further react to form hematite.

[0012] Furthermore, in step 1, the deionized water washing involves ultrasonically dispersing the obtained solid precipitate into deionized water at a solid-liquid ratio of 1:10, ultrasonically washing for 10 minutes, centrifuging after washing, and removing the supernatant. This step is repeated 3 to 10 times until the supernatant is clear and transparent.

[0013] Furthermore, the nanorod-shaped nanorods described in step 1 β -FeOOH has a size length of 400 nm to 1.5 μm. β -FeOOH nanorods have the same width and height, with a size range of 20 nm to 60 nm.

[0014] Furthermore, the nanorod-shaped nanorods of step 2 β -FeOOH is fully dispersed in deionized water, in nanorod form. β The concentration of -FeOOH is 0.03–0.08 mol / L.

[0015] Furthermore, the nanorod-shaped nanorods of step 2 β-FeOOH is fully dispersed in deionized water by ultrasonic dispersion for 10-20 min.

[0016] Furthermore, in step 2, the pH range of the hydrochloric acid adjustment solution is 1 to 3. The pH is mainly used to control the morphology of the hematite to be curved twin crystals.

[0017] Furthermore, the hydrothermal reaction temperature in step 2 is 180℃~230℃, and the reaction time is 18~32 h. If the temperature is below 180℃ or above 230℃, the morphology of hematite will not be a curved twin crystal. If the reaction time is less than 18 h, the reaction is incomplete, and rod-shaped products will exist; if the reaction time is too long, the curved twin crystals will agglomerate and recrystallize into larger, irregular morphologies.

[0018] Furthermore, in step 2, the deionized water cleaning involves ultrasonically dispersing the obtained solid precipitate into deionized water at a solid-liquid ratio of 1:10, and then performing ultrasonic cleaning 3 to 10 times.

[0019] This invention utilizes FeCl3·6H2O solution to obtain nanorod-shaped nanoparticles through a static reaction in an oven. β -FeOOH precipitate, then used in nanorod form β The FeOOH precipitate was thoroughly mixed with deionized water of different pH values, within the pH range of 1 to 3. β -FeOOH is fully dispersed and reacted via a hydrothermal method to generate a nano-hematite curved twin crystal. The effect of acid alters... β -FeOOH surface sites regulate the morphology of hematite formation.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention is the first to achieve the artificial synthesis of hematite nano-curved twin crystals in the laboratory. It provides a new method for the preparation and research of a relatively special morphology of hematite material, which contains 12 curved symmetrical flying saucer-shaped twin crystals.

[0022] The method for preparing nano-hematite curved surface twins provided by this invention is a one-step hydrothermal reaction method, which is convenient to operate and has the advantages of reproducibility.

[0023] This invention provides a green synthesis method for nanoscale curved twinned hematite without the addition of excess surfactants, solving the problem that existing technologies cannot synthesize nanoscale curved twinned hematite.

[0024] This invention can further enrich the synthesis methods of hematite, while eliminating the need for the addition of organic solvents, surfactants and other substances. It is green, environmentally friendly, and simple in process, and can achieve large-scale preparation. Attached Figure Description

[0025] Figure 1 β XRD patterns of FeOOH (left) and Fe2O3 (right);

[0026] Figure 2 Scanning electron microscope image of a 500 nm resolution nano-hematite curved double crystal prepared in Example 1;

[0027] Figure 3 The image shows a scanning electron microscope (SEM) image of a 1 μm resolution nano-hematite curved twin crystal prepared in Example 2. Detailed Implementation

[0028] The technical solution of the present invention will be further described in detail below through embodiments. These embodiments are intended to explain the present invention and not to limit it. Example 1

[0029] Step 1: Under continuous stirring, 0.405 g of FeCl3·6H2O was dissolved in 50 mL of deionized water to obtain a 0.03 mol / L ferric chloride solution. The ferric chloride solution was placed in a reaction flask and placed in an oven at 65℃ for 5 days to react. The precipitate after the reaction was collected, washed three times with deionized water, and dried in an oven at 30℃ to obtain nanorod-shaped nanorods. β -FeOOH, XRD pattern of product is shown in [reference needed]. Figure 1 a.

[0030] Step 2, weigh 0.1335 g β -FeOOH mineral powder was dispersed in 50 mL of hydrochloric acid aqueous solution with a pH of 1. β The concentration of -FeOOH was 0.03 mol / L. It was ultrasonically dispersed in deionized water for 10 min, then added to a reaction vessel and placed in an oven at 180℃ for a hydrothermal reaction for 18 h. After the reaction vessel cooled to room temperature, the resulting solid was washed with deionized water and dried to obtain hematite nano-curved twin crystals. The hematite yield was 0.029 mol / L and 4.64 g / L, with a synthesis efficiency of 96.6%. The XRD pattern of the product is shown below. Figure 1 b. Scanning electron microscopy at a resolution of 500 nm was performed on it; the results are shown in [Figure number missing]. Figure 2 .like Figure 2 The scanning electron microscope images shown indicate that the obtained sample is composed of nano-sized hematite curved twin crystals, and the nano-sized hematite crystal faces are clearly visible, indicating that we have successfully prepared nano-sized hematite curved twin crystals using this method. Example 2

[0031] Step 1: Under continuous stirring, 1.08 g of FeCl3·6H2O was dissolved in 50 mL of deionized water to obtain a 0.08 mol / L ferric chloride solution. The ferric chloride solution was placed in a reaction flask and placed in an oven at 85℃ for 8 days. The resulting precipitate was washed 10 times with deionized water and dried to obtain nanorod-shaped particles. β -FeOOH;

[0032] Step 2, weigh 0.356 g β -FeOOH mineral powder was dispersed in 50 mL of hydrochloric acid aqueous solution with a pH of 3. β The concentration of -FeOOH was 0.08 mol / L. It was ultrasonically dispersed in deionized water for 10 min, then added to a reaction vessel and placed in an oven at 230℃ for a hydrothermal reaction for 32 h. After the reaction vessel cooled to room temperature, the resulting solid was washed with deionized water and dried to obtain hematite nano-curved twin crystals. The hematite yield was 0.079 mol / L and 12.64 g / L, with a synthesis efficiency of 96.6%. XRD patterns are shown below. Figure 1 b. The sample was observed using a scanning electron microscope with a resolution of 1 μm. The results are shown in [Figure number missing]. Figure 3 .like Figure 3 The scanning electron microscope images shown indicate that the obtained sample is composed of nano-hematite curved twin crystals. The crystal faces and morphological distribution of the hematite particles are clearly visible, indicating that we have successfully prepared nano-hematite curved twin crystals using this method. Example 3

[0033] Step 1 is the same as in Example 1.

[0034] Step 2, weigh 0.1335 g β -FeOOH mineral powder was dispersed in 50 mL of hydrochloric acid aqueous solution with a pH of 0.5. β The concentration of -FeOOH was 0.03 mol / L. It was ultrasonically dispersed in deionized water for 10 min, and then added to a reaction vessel and placed in an oven at 180℃ for hydrothermal reaction for 18 h. After the reaction vessel cooled to room temperature, the generated solid material was washed and dried with deionized water. The product was irregularly shaped spherical nanoparticles, and hematite with nano-curved bicrystalline morphology was not obtained. Example 4

[0035] Step 1 is the same as in Example 1.

[0036] Step 2, weigh 0.1335 g β -FeOOH mineral powder was dispersed in 50 mL of hydrochloric acid aqueous solution with a pH of 4.5. βThe concentration of -FeOOH was 0.03 mol / L. It was ultrasonically dispersed in deionized water for 10 min, and then added to a reaction vessel and placed in an oven at 180℃ for hydrothermal reaction for 18 h. After the reaction vessel cooled to room temperature, the generated solid material was washed and dried with deionized water to obtain hematite with a morphology of oblique tetrahedron and without nano-curved bicrystalline morphology.

[0037] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing nano-curved twinned hematite, characterized in that, The steps include the following: Step (1) Under continuous stirring, FeCl3·6H2O was dissolved in deionized water to obtain a ferric chloride solution. The ferric chloride solution was added to a reaction flask and sealed. The reaction was carried out at a temperature of 65℃~85℃ for 5~9 days. The precipitate obtained was washed with deionized water and dried to obtain nanorods. β -FeOOH; Step (2) is to obtain the result from step (1) β -FeOOH is fully dispersed in deionized water to obtain β -FeOOH aqueous solution; adjust the pH of the solution to 1~3 with hydrochloric acid, and then carry out a hydrothermal reaction at a temperature of 180℃~230℃ for 18~32 h. After cooling to room temperature, wash and dry the solid material with deionized water to obtain hematite nano-curved twin crystals.

2. The method for synthesizing nano-curved twinned hematite according to claim 1, characterized in that, The concentration of FeCl3·6H2O in step (1) is 0.03 to 0.08 mol / L.

3. The method for synthesizing nano-curved twinned hematite according to claim 1, characterized in that, The reaction in step (1) is a static reaction.

4. The method for synthesizing nano-curved twinned hematite according to claim 1, characterized in that, The nanorod-shaped β -FeOOH has a length of 400 nm to 1.5 μm; its width and height are the same, with a size of 20 nm to 60 nm.

5. The method for synthesizing nano-curved twinned hematite according to claim 1, characterized in that, Step (2) β The concentration of the FeOOH aqueous solution is 0.03–0.08 mol / L.

6. The method for synthesizing nano-curved twinned hematite according to claim 1, characterized in that, The hydrothermal reaction in step (2) is carried out in a rotary oven in a reactor.

7. A nano-curved twinned hematite synthesized using the method described in any one of claims 1-6, characterized in that, The nano-curved twinned hematite has a symmetrical saucer-shaped twinned structure containing 12 curved surfaces.

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