Array type mesoporous iron oxide nanorod and preparation method thereof

Abstract

The invention belongs to the technical field of mesoporous materials, and discloses a preparation method of array type mesoporous iron oxide nanorods. The method specifically comprises the following steps: mixing P123, glycerol, ferric chloride hexahydrate, concentrated hydrochloric acid and deionized water, stirring in a water bath, adding TEOS after a period of time, continuously stirring, stopping stirring after a period of time, and standing; and carrying out hydrothermal treatment on the obtained mixture, washing, drying, and removing the template agent and the structure-directing agent through calcination and alkali washing to finally prepare the target product. The mesoporous iron oxide nanorod prepared by the method has a regular array type characteristic, the length of the nanorod is about 200nm, the diameter of the nanorod is about 30nm, and the nanorod has a mesoporous structure with the average pore diameter of about 15nm. The nanorod has excellent active site exposure degree and loading adaptability, so that the nanorod has a wide application prospect in the fields of catalytic degradation, heavy metal adsorption and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mesoporous materials, and particularly relates to a preparation method of array type mesoporous iron oxide nanorods. BACKGROUND

[0002] The mesoporous iron oxide retains the inherent properties of iron oxide, and significantly improves the number of surface active sites and the material diffusion efficiency by virtue of the high specific surface area and open pores of the mesoporous structure, effectively solving the problems of easy agglomeration, large mass transfer resistance and the like of traditional iron oxide materials in the reaction. The early preparation of mesoporous iron oxide faces problems such as complex crystal phase, easy formation of hydroxyl iron oxide (such as alpha-FeOOH, beta-FeOOH) and skeleton collapse, and with the application of soft and hard template methods, the preparation technology has gradually developed, laying a foundation for subsequent research.

[0003] Compared with other morphologies of mesoporous iron oxide such as irregular ellipsoidal, layered and microspherical, the mesoporous iron oxide nanorods have obvious advantages: the nanorods combined with the mesoporous structure can improve the specific surface area, provide more active sites and enhance the performance of adsorption and catalysis and the like. The hydrothermal method combined with the template regulation process used in the present application can prepare the mesoporous iron oxide nanorods with obvious mesoporous structure and array type structure, and the mesoporous distribution is more uniform, without complex template or high temperature treatment, effectively solving the problems of poor controllability of morphology and uneven mesoporous distribution in the traditional method, and providing a new scheme with simple process and adjustable parameters for the large-scale preparation of mesoporous metal oxides. SUMMARY

[0004] In view of the problems of complex preparation process, difficult morphology and mesoporous structure regulation of the existing mesoporous iron oxide nanorods, the present application provides a preparation method of array type mesoporous iron oxide nanorods, which realizes the accurate regulation of mesoporous pore size, rod size and array arrangement through the synergistic effect of the template agent and the structure directing agent, and prepares the nanorods with array structure.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical scheme: The array type mesoporous iron oxide nanorod of the present application has a rod-like array morphology with mesoporous structure, the length of the nanorod is about 200 nm, the diameter is about 30 nm, the central axes of the nanorods in the array are parallel to each other, and the mesoporous structure has an average pore size of about 15 nm.

[0006] The preparation method of the array type mesoporous iron oxide nanorod of the present application comprises the following steps: Step 1: (1) Prepare a 10% P123 surfactant clear aqueous solution, and the molecular weight of P123 is 5800; (2) adding deionized water, urea, ferric chloride hexahydrate, hydrochloric acid and glycerol, wherein the mass ratio of urea to P123 is (35-55:1), the mass ratio of ferric chloride hexahydrate to P123 is (4.5-11.5:1), and the mass ratio of glycerol to P123 is (4-8:1); (3) placing the above reagents in a water bath, the water bath temperature is 25-35℃, and stirring to mix uniformly to obtain a mixed solution; Step 2: (1) after stirring for a period of time, adding TEOS into the above mixed solution, wherein the reaction time of the solution before adding TEOS is 10-20 min, and the mass ratio of TEOS to P123 is (0.5-5:1); (2) continuing to stir after adding TEOS into the mixed solution, stopping stirring after a period of time, and placing in a 40℃ water bath to stand; Step 3: (1) transferring the solution after standing into a polytetrafluoroethylene liner, and then placing in a hydrothermal synthesis reaction kettle, and then placing in an oven with a temperature of 100-140℃ to perform hydrothermal treatment, and taking out the product after 20-28 h; (2) extracting, washing, drying and calcining the product to remove the template agent; Step 4: (1) preparing a NaHCO3 solution with a concentration of 0.24 mol / L as an etching solution to remove the silicon dioxide in the mesoporous iron oxide nanorod, and placing the product into the etching solution and placing in a 50℃ water bath to continuously stir for 8-16 h; (2) extracting, washing and drying the product after etching, and then performing secondary etching according to the same conditions to sufficiently remove the silicon dioxide in the mesoporous iron oxide nanorod. After etching, the product is extracted, washed and dried again, and finally the array type mesoporous iron oxide nanorod is prepared.

[0007] Wherein: The deionized water in step 1(2) is 78 g, and the hydrochloric acid is 0.5 g.

[0008] The TEOS in step 2(1) is tetraethyl orthosilicate, the stirring time in step 2(2) is 2-6 h, and the standing time is 2-8 h.

[0009] The drying temperature in step 3(2) is 50℃, the calcination temperature is 550℃, and the calcination holding time is 4 h.

[0010] Compared with the prior art, the preparation method of the array type mesoporous iron oxide nanorod has the beneficial effects that: (1) The preparation system of the present invention is relatively simple: only surfactant (P123) is used as a soft template and TEOS is used as a structure directing agent, without involving the use of other organic or inorganic additives; (2) The preparation process of the present invention is relatively simple: the preparation process adopts a one-step hydrothermal method, which does not involve complex multi-step reaction or separation and purification steps; (3) The present invention can achieve coordinated control of the orderliness of the array structure, the rod-shaped morphology and the mesoporous structure by adjusting parameters such as the amount of TEOS added and the hydrothermal time. Attached Figure Description

[0011] Figure 1 Scanning electron microscope (SEM) images of different array-type mesoporous iron oxide nanorods prepared in Examples 1, 2, and 3 of this invention at different magnifications; wherein, Figures A1-A3 are SEM images of RNMIs-1 prepared in Example 1 at different magnifications; Figures B1-B3 are SEM images of RNMIs-2 prepared in Example 2 at different magnifications; Figures C1-C3 are SEM images of RNMIs-3 prepared in Example 3 at different magnifications; Figure 2 Pore ​​size distribution diagrams of different array-type mesoporous iron oxide nanorods prepared in Examples 1, 2 and 3 of this invention; wherein, Figure A is the pore size distribution diagram of RNMIs-1 prepared in Example 1; Figure B is the pore size distribution diagram of RNMIs-2 prepared in Example 2; and Figure C is the pore size distribution diagram of RNMIs-3 prepared in Example 3. Figure 3 The nitrogen adsorption-desorption curves of mesoporous iron oxide nanorods with different array types prepared in Examples 1, 2 and 3 of this invention are shown in Figure a. Figure a shows the nitrogen adsorption-desorption curve of RNMIs-1 prepared in Example 1; Figure b shows the nitrogen adsorption-desorption curve of RNMIs-2 prepared in Example 2; and Figure c shows the nitrogen adsorption-desorption curve of RNMIs-3 prepared in Example 3. Detailed Implementation

[0012] Example 1 An array of mesoporous iron oxide nanorods, such as Figure 1 As shown in (A2, A3), the nanorods have a diameter of 25–30 nm and a length of approximately 200 nm, and are arranged in a relatively dense array. The specific surface area is 59.5 m². 2 / g; Step 1: (1) Prepare a 2g clear aqueous solution of P123 surfactant with a mass fraction of 10% and a molecular weight of 5800; (2) Add 78g deionized water, 9g urea, 2.1g ferric chloride hexahydrate, 0.5g hydrochloric acid and 1.2g glycerol; (3) The above reagent is placed in a water bath, the water bath temperature is 30℃, and the mixture is stirred and mixed uniformly to obtain a mixed solution; Step 2: (1) After stirring for 15 min, 0.1 g of TEOS is added to the mixed solution; (2) After adding TEOS to the mixed solution, stirring is continued for 4 h; (3) The stirring is stopped, and the solution is left to stand in a water bath at 40℃ for 4 h; Step 3: (1) The solution after standing is transferred into a polytetrafluoroethylene liner, which is then placed in a hydrothermal synthesis reactor, and then placed in an oven at a temperature of 120℃ for hydrothermal treatment. The product is taken out after 24 h; (2) The product is suction filtered, washed, and dried in an oven at 50℃, and then subjected to calcination treatment at a calcination temperature of 550℃ for 4 h to remove the template agent; Step 4: (1) A NaHCO3 solution with a concentration of 0.24 mol / L is prepared as an etching solution to remove the silica in the mesoporous iron oxide nanorod. The product is poured into the etching solution and placed in a 50℃ water bath for continuous stirring for 12 h; (2) The product after etching is subjected to suction filtration, washing, and drying treatment, and then subjected to secondary etching under the same conditions as above to fully remove the silica in the mesoporous iron oxide nanorod. After etching is completed, the product is again subjected to suction filtration, washing, and drying, and finally the array-type mesoporous iron oxide nanorod is prepared and named RNMIs-1; The array-type mesoporous iron oxide nanorod RNMIs-1 prepared in this example has a nitrogen adsorption-desorption curve as shown in Figure 1 (A1), which shows that the array is composed of isotropic and closely fitted rod-shaped nanometer iron oxide, and clear and well-connected mesopores exist on each nanorod; Figure 3 The nitrogen adsorption-desorption curve of (a line) shows that the curve belongs to type IV isotherm, indicating that it belongs to a system in which a porous adsorbent appears capillary condensation. There is no obvious adsorption saturation platform, and the adsorption amount increases sharply in the high relative pressure region. Combined with the pore size distribution data of (A), it can be known that the mesopore size is mainly concentrated around 15 nm, and it also shows that the mesoporous structure is complex, the pore size distribution is wide, and the overall array morphology and rich pore structure characteristics are presented. Figure 2

[0013] Example 2 An array-type mesoporous iron oxide nanorod, as shown in Figure 1 (B2, B3), has a nanorod diameter of 30-40 nm, a length of about 200 nm, and a relatively wide end. The array-type structure is irregular. The specific surface area is 54.6 m 2 / g; ​Step 1: (1) A 2g mass fraction of 10% P123 surfactant clear aqueous solution was configured, and the molecular weight of P123 was 5800; (2) 78g of deionized water, 9g of urea, 2.1g of ferric chloride hexahydrate, 0.5g of hydrochloric acid and 0.6g of glycerol were added; (3) The above reagents were placed in a water bath, the water bath temperature was 30℃, and the mixture was stirred and mixed uniformly to obtain a mixed solution; Step 2: (1) After stirring for 15min, 0.1g of TEOS was added to the mixed solution; (2) After adding TEOS to the mixed solution, continue to stir for 8h; (3) Stop stirring and stand in a 40℃ water bath for 4h; Step 3: (1) The standing solution was transferred into a polytetrafluoroethylene liner and then placed into a hydrothermal synthesis reactor, and then placed into an oven with a temperature of 120℃ for hydrothermal treatment. The product was taken out after 24h; (2) The product was suction filtered, washed, and dried in an oven at 50℃, and then subjected to calcination treatment at a calcination temperature of 550℃ for 4h to remove the template agent; Step 4: (1) A 0.24mol / L NaHCO3 solution was prepared as an etching solution to remove the silica in the mesoporous iron oxide nanorod. The product was poured into the etching solution and placed in a 50℃ water bath for continuous stirring for 12h; (2) The product after etching was suction filtered, washed, and dried, and then subjected to secondary etching under the same conditions as above to fully remove the silica in the mesoporous iron oxide nanorod. After etching, the product was again suction filtered, washed, and dried, and finally an array type mesoporous iron oxide nanorod was prepared, which was named RNMIs-2; The array type mesoporous iron oxide nanorod RNMIs-2 prepared in this example has a uniform array type morphology and a rich mesoporous structure, and the mesoporous structure is mainly concentrated on the end of the nanorod. Figure 1 (B1, B2) It can be seen that the mesopores are concentrated on the end of the nanorod, and the mesopores on the side of the rod are less, Figure 3 The nitrogen adsorption-desorption curve in (b line) is a type IV isotherm, proving that it belongs to a mesoporous structure. And there is no obvious adsorption saturation platform feature, combined with Figure 2 The pore size distribution data of (B) shows that the mesopore size is mainly concentrated around 12nm, which reflects the characteristics of complex pore structure and wide pore size distribution of the material, and the overall presents a unique array type morphology and rich mesoporous structure characteristics.

[0014] Example 3 An array type mesoporous iron oxide nanorod, such as Figure 1The nanorod diameter is 30-50 nm, the length is about 230 nm, the array type structure is irregular, and the nanorod is spindle-shaped. The specific surface area is 134.8 m 2 / g; Step 1: (1) 2 g of a 10% P123 surfactant clear aqueous solution with a molecular weight of 5800; (2) 78 g of deionized water, 9 g of urea, 2.1 g of iron chloride hexahydrate, 0.5 g of hydrochloric acid and 1.2 g of glycerol are added; (3) The above reagents are placed in a water bath, the water bath temperature is 30 DEG C, and the mixture is uniformly stirred and mixed to obtain a mixed solution; Step 2: (1) After stirring for 15 min, 0.8 g of TEOS is added to the mixed solution; (2) After adding TEOS to the mixed solution, continue to stir for 8 h; (3) Stop stirring and stand in a 40 DEG C water bath for 4 h; Step 3: (1) The solution after standing is transferred into a polytetrafluoroethylene liner and then placed in a hydrothermal synthesis reactor, and then placed in an oven at a temperature of 120 DEG C for hydrothermal treatment. The product is taken out after 24 h; (2) The product is suction filtered, washed, dried in an oven at 50 DEG C, and then calcined at a temperature of 550 DEG C for 4 h to remove the template; Step 4: (1) A NaHCO3 solution with a concentration of 0.24 mol / L is prepared as an etching solution to remove the silica in the mesoporous iron oxide nanorod. The product is poured into the etching solution and stirred in a 50 DEG C water bath for 12 h; (2) The product after etching is suction filtered, washed and dried, and then subjected to secondary etching under the same conditions as above to fully remove the silica in the mesoporous iron oxide nanorod. After etching, the product is suction filtered, washed and dried again, and finally the array type mesoporous iron oxide nanorod is obtained, which is named RNMIs-3; The array type mesoporous iron oxide nanorod RNMIs-3 prepared in this embodiment has a two-level mesoporous structure, which is characterized by Figure 1 (C1) The rod bodies are arranged relatively loosely, Figure 3 The nitrogen adsorption-desorption curve of (c line) shows no obvious adsorption saturation platform characteristics, and the adsorption amount gradually increases with the increase of relative pressure (P / P0). In the high relative pressure region, the adsorption amount increases significantly, which belongs to the IV type H3 type hysteresis loop isotherm, which indicates that the pore structure of the material is complex; combined with Figure 2The pore size distribution data of (C) shows that the mesopore size is mainly concentrated in 4 nm and 52 nm. According to the analysis of the electron microscope image and the pore size distribution graph, the 52 nm pore size is closely related to the accumulation mode of the nanorods and the gap between the particles. The electron microscope image shows that the nanorods are arrayed, but there is a phenomenon of loose accumulation of the rod bodies in the local area. The rod and the rod do not form close contact, but there is a larger gap space. When the rod bodies are loosely accumulated, the surface distance between the adjacent rod bodies is enlarged, and then a large size channel of about 52 nm is formed.

Claims

1. A method for preparing array-type mesoporous iron oxide nanorods, characterized in that, Specifically, the following steps are included: Step 1: (1) Prepare a clear aqueous solution of P123 surfactant with a mass fraction of 10% and a molecular weight of 5800; (2) Add deionized water, urea, ferric chloride hexahydrate, hydrochloric acid and glycerol, wherein the mass ratio of urea to P123 is (35-55:1), the mass ratio of ferric chloride hexahydrate to P123 is (4.5-11.5:1), and the mass ratio of glycerol to P123 is (4-8:1). (3) Place the above reagents in a water bath at a temperature of 25-35°C and stir until homogeneous to obtain a mixture. Step 2: (1) After stirring for a period of time, add TEOS to the mixed solution. The reaction time of the solution before adding TEOS is 10 to 20 min. The mass ratio of TEOS to P123 is (0.5 to 5:1). (2) Add TEOS to the mixed solution and continue stirring. After a period of time, stop stirring and place it in a water bath at 40°C for standing treatment. Step 3: (1) After the solution has been allowed to stand, it is transferred into a polytetrafluoroethylene liner and then placed into a hydrothermal synthesis reactor. After that, it is placed in an oven at a temperature of 100-140℃ for hydrothermal treatment. After 20-28 hours, the product is taken out. (2) The product is filtered, washed, dried, and calcined to remove the template agent. The drying is carried out at 50°C, the calcination temperature is 550°C, and the holding time is 4h. Step 4: (1) Prepare a NaHCO3 solution with a concentration of 0.24 mol / L as an etching solution to remove silica from mesoporous iron oxide nanorods. Pour the product into the etching solution and place it in a 50℃ water bath and stir continuously for 8 to 16 hours. (2) The etched product is filtered, washed and dried. Then, it is etched again under the same conditions to remove silicon dioxide from the mesoporous iron oxide nanorods. After the second etching is completed, the product is filtered, washed and dried again to finally obtain an array of mesoporous iron oxide nanorods with a mesoporous structure. The central axes of the nanorods in the array are parallel to each other, with a length of about 200 nm and a diameter of about 30 nm.

2. The preparation method according to claim 1, characterized in that, The stirring time in step 2(2) is 2 to 6 hours, and the settling time is 2 to 8 hours.

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