CN111732129B

CN111732129B - Preparation method and application of oxygen-assisted double hydroxide self-assembled thin-layer layered structure

Info

Publication number: CN111732129B
Application number: CN202010032894.8A
Authority: CN
Inventors: 邓意达; 赵君; 韩晓鹏; 胡文彬; 陈亚楠; 张金凤; 钟澄
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2020-01-13
Filing date: 2020-01-13
Publication date: 2023-04-07
Anticipated expiration: 2040-01-13
Also published as: CN111732129A

Abstract

The invention discloses a preparation method and application of a self-assembled thin-layer layered structure of double hydroxide assisted by oxygen, which comprises the steps of respectively weighing metal salts, dissolving the metal salts in saturated oxygen deionized water, uniformly stirring in an oxygen atmosphere, uniformly stirring and dispersing, adding an alkali solution, adjusting the flow rate of oxygen and stirring to obtain a precipitate; and centrifugally cleaning the precipitate by using deionized water and absolute ethyl alcohol, and drying by using a vacuum oven to obtain the nano-scale powder material. The preparation method is simple, simple and convenient to operate, low in cost and good in industrial application prospect.

Description

Preparation method and application of oxygen-assisted double hydroxide self-assembled thin-layer layered structure

Technical Field

The invention belongs to the field of material science and engineering, and particularly relates to a preparation method of a nano catalytic material in the field of electrocatalysis, in particular to a preparation method of a thin-layer layered structure by self-assembly of double hydroxides through oxygen assistance.

Background

Layered metal hydroxides (LDHs) are intercalation materials, anions are easily adhered to the surface, a main layer of a crystal structure is a host layer with positive charges, hydroxide ions are arranged between layers, and due to the unique structural combination characteristic, the materials have the characteristics of being capable of adsorbing anions, being peelable, being self-assembled with other materials and being topologically transformed in structure, can be used as a catalyst, a catalyst carrier or a precursor, and have wide application prospects in the field of heterogeneous catalysis. The control of the morphology can have an effect on the electrocatalytic properties, as the morphology can affect the surface structure of the LDHs and the chemical environment around the metal ions, etc.

Two-dimensional thin-layer catalysts have received much attention as a new class of nanomaterials. Due to the thin two-dimensional structure, the material is obviously superior to the corresponding bulk material in the aspects of physical, chemical and electronic properties and the like. In the field of catalysis, thin layer catalysts have several unique advantages: first, the two-dimensional thin layer material has a larger specific surface area under the same volume, so that more target molecules can be adsorbed on the two-dimensional thin layer material. On the other hand, the thin layer thickness can shorten the diffusion distance of charges from the inside to the surface, the accessibility of electrons to electrons can be improved to the maximum extent, the transmission resistance of interface electrons is reduced in the electrocatalysis process, the electron transmission is accelerated, the material conductivity is improved, meanwhile, the electrons can be rapidly transmitted in a two-dimensional structure plane, the electron mobility is high, and therefore the electrocatalysis process is facilitated. In addition, a large number of unsaturated coordination ions exist on the surface of the thin-layer two-dimensional nano material, so that the chemical environment of the active center of the metal ions can be changed, the metal ions participate in the interface catalytic reaction, and the number of reactive sites is increased.

The synthesis of two-dimensional thin-layer structure LDHs is a challenge, and at present, the thin-layer LDHs material can be prepared by two conventional methods, namely bottom-up method or top-down method. The bottom-up method mainly comprises a template method, electrodeposition and solvothermal, and the top-down method is usually realized by stripping thick layers of LDHs. The methods are difficult to realize one-step simple synthesis and large-scale preparation, and cannot meet the industrial production requirements. The wet chemical method is a simple synthesis mode which is easy to produce in quantity and has a short period, but is difficult to synthesize the thin-layer LDHs.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a preparation method and application of a transition metal double hydroxide nano film material (namely a preparation method for self-assembling a thin layer laminated structure through oxygen-assisted double hydroxide). Oxygen is introduced by adopting a wet chemical method, the thin-layer LDHs is prepared by promoting the growth of a transverse crystal face through the oxygen, the preparation method is simple, and the prepared transition metal hydroxide is a thin-film nano material with the thickness of 150-200 nm and is below 5nm, so that a larger specific surface area can be provided for catalytic reaction. The method can realize mass preparation and has good application prospect in the industrial application fields of energy storage, conversion and the like. So far, the method for preparing transition metal double hydroxide by introducing oxygen by a wet chemical method has not been reported at home and abroad.

The technical purpose of the invention is realized by the following technical scheme:

a preparation method of a thin-layer laminated structure self-assembled by double hydroxide assisted by oxygen comprises the following steps:

step 1, weighing two transition metal salts, uniformly dispersing the two transition metal salts in deionized water containing saturated oxygen, and stirring and dissolving the two transition metal salts in an oxygen protective atmosphere to form a transparent solution;

in step 1, the transition metal salt is a cobalt salt such as cobalt nitrate, cobalt chloride, or cobalt acetate, a nickel salt such as nickel nitrate, nickel chloride, or nickel acetate, a vanadium salt such as vanadium chloride, or a manganese salt such as manganese nitrate or manganese acetate.

In step 1, the amount of the transition metal salt is 3 to 15mmol, and the ratio of the two transition metal salts is (3 to 5): 1.

in the step 1, continuously introducing oxygen into deionized water to form a saturated solution; the flow rate of oxygen is 70-100 mL/min.

Step 2, pouring alkali liquor into the transparent solution obtained in the step 1, keeping the saturated oxygen state of the liquid, and stirring in an oxygen protective atmosphere to obtain a precipitate; the stirring speed is 300-500 r/min, and the stirring time is 60-180 min;

in the step 2, the alkali liquor is an aqueous solution of sodium hydroxide or potassium hydroxide, and the concentration is 2-5 mol/L.

In the step 2, the stirring speed is 350-450 r/min, and the stirring time is 100-150 min.

In the step 2, oxygen is continuously introduced into the deionized water to form a saturated solution, and the flow rate of the oxygen is 100-150 mL/min.

And 3, washing the precipitate obtained in the step 2 by deionized water and absolute ethyl alcohol in sequence, and drying in a vacuum oven to obtain the few-layer transition metal double hydroxide nano thin-layer material.

In the step 3, the vacuum drying temperature is 25-50 ℃, and the vacuum drying time is 10-20 h.

In the preparation method, oxygen is continuously introduced into deionized water in the whole reaction process to form a saturated solution and provide oxygen for the reaction atmosphere; and simultaneously placing the deionized water with saturated oxygen in an oxygen protective atmosphere.

The application of the preparation method in preparing the double-hydroxide self-assembled thin layer achieves a two-dimensional structure, the size reaches hundreds of nanometers, such as 100-300 nm, and the thickness is below 5nm.

The invention discloses a method for synthesizing thin-layer LDHs by an oxygen-assisted wet chemical method, which is simple and rapid to operate, can be used for large-scale preparation and can meet the requirements of practical application. The saturated oxygen environment can enable the crystal faces which are easy to absorb oxygen after the materials are nucleated to absorb enough oxygen, so that the crystal faces are prevented from growing, the other crystal faces grow, a larger thin-layer two-dimensional structure is formed, and the size reaches hundreds of nanometers. The method is used for successfully preparing the cobalt-vanadium, cobalt-manganese and cobalt-nickel few-layer double metal hydroxide material with the thickness of below 5 nanometers. Compared with the prior art, the invention has the following beneficial effects: (1) The preparation method of the invention has the advantages of simple required equipment conditions, convenient operation and low preparation cost, and is suitable for industrial large-scale production; (2) The method adopts a one-step liquid phase method to prepare the transition metal double hydroxide nano film material by simultaneously flowing oxygen in parallel, has high repeatability, can effectively ensure the shape control of the product, and greatly simplifies the preparation process flow.

Drawings

FIG. 1 is an X-ray diffraction diagram of the cobalt vanadium double hydroxide nano material prepared by the method.

FIG. 2 is an X-ray diffraction diagram of the cobalt manganese double hydroxide nano material prepared by the method.

FIG. 3 is an X-ray diffraction diagram of the cobalt-nickel double hydroxide nano material prepared by the method.

FIG. 4 is a transmission electron microscope image of the cobalt vanadium double hydroxide nano-material prepared by the method.

FIG. 5 is a transmission electron microscope image of the cobalt manganese double hydroxide nano material prepared by the method.

FIG. 6 is a transmission electron microscope image of the cobalt nickel double hydroxide nano-material prepared by the method.

FIG. 7 is an atomic force microscope image of the cobalt vanadium double hydroxide nano-material prepared by the method.

FIG. 8 is an atomic force microscope image of the cobalt manganese double hydroxide nano-material prepared by the method.

FIG. 9 is an atomic force microscope image of the cobalt-nickel double hydroxide nanomaterial prepared by the method.

FIG. 10 is a schematic flow chart of the preparation method of the present invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the concept of the invention. All falling within the scope of the present invention.

Example 1

(1) Weighing 12mmol of cobalt nitrate and 4mmol of vanadium chloride, dissolving in 50mL of deionized water containing saturated oxygen, stirring and dissolving in an oxygen protective atmosphere, wherein the flow rate of oxygen gas is 70mL/min, and forming a transparent solution.

(2) And (3) quickly adding 25mL of 2mol/L sodium hydroxide into the suspension, adjusting the flow rate of oxygen to be 80mL/min, stirring at the rotation speed of 500r/min for 30min, and obtaining brown precipitate.

(3) And sequentially washing the brown precipitate with deionized water and absolute ethyl alcohol for three times respectively, and drying in a vacuum oven at 30 ℃ for 15h to obtain the nano film cobalt-vanadium double hydroxide material.

FIG. 1 is the X-ray diffraction pattern of the cobalt-vanadium double hydroxide material prepared in this example, from which it can be seen that the prepared material has very good peak of hydrotalcite structure characteristic, and the main phase crystal structure is a-Co (OH) ₂ And further contains vanadium.

FIG. 4 is a transmission electron micrograph of the cobalt vanadium double hydroxide material prepared in this example, which shows that the cobalt vanadium double hydroxide is in the form of a thin film of about 150 to 200nm.

FIG. 7 is an atomic force microscope image of the cobalt vanadium double hydroxide nano-material prepared by the method, and the thickness analysis is about 2nm.

Example 2

(1) Weighing 12mmol of cobalt nitrate and 4mmol of manganese acetate, dissolving the cobalt nitrate and the manganese acetate in 50mL of deionized water with saturated oxygen, and stirring the mixture to dissolve the cobalt nitrate and the manganese acetate in an oxygen protective atmosphere at an oxygen gas flow rate of 70mL/min to form a transparent solution.

(2) And (3) quickly adding 20mL of 2mol/L sodium hydroxide into the mixed suspension, adjusting the flow rate of oxygen to be 80mL/min, stirring at the rotation speed of 500r/min for 1.5h, and obtaining a dark brown precipitate.

(3) And sequentially washing the brown precipitate with deionized water and absolute ethyl alcohol for three times respectively, and drying in a vacuum oven at 30 ℃ for 15 hours to obtain the nano film cobalt-manganese double hydroxide material.

Fig. 2 is an X-ray diffraction spectrum of the cobalt-manganese double hydroxide material prepared in this example, and it can be seen from the figure that the main phase crystal structure of the prepared material corresponds to CoO (OH), and further contains manganese element.

FIG. 5 is a transmission electron micrograph of the cobalt manganese double hydroxide material prepared in this example, which shows that the prepared material is a film with significant wrinkles on the surface, about 200 to 300nm.

FIG. 8 is an atomic force microscope image of the cobalt manganese double hydroxide nano-material prepared by the method, and the thickness analysis is about 3.5nm.

Example 3

(1) Weighing 12mmol of cobalt nitrate and 3mmol of nickel nitrate, dissolving in 50mL of deionized water containing saturated oxygen, stirring and dissolving in an oxygen protective atmosphere, wherein the flow rate of oxygen gas is 70mL/min, and forming a transparent solution.

(2) And (3) quickly adding 20mL of 2mol/L sodium hydroxide into the mixed suspension, adjusting the flow of oxygen to be 100mL/min, stirring at the rotating speed of 600r/min for 0.5h, and obtaining dark green precipitate.

(3) And (3) sequentially washing the dark green precipitate with deionized water and absolute ethyl alcohol for three times respectively, and drying in a vacuum oven at 35 ℃ for 20 hours to obtain the nano film cobalt-nickel double hydroxide material.

FIG. 3 is the X-ray diffraction pattern of the cobalt-nickel double hydroxide material prepared in this example, from which it can be seen that the main phase crystal structure of the prepared material corresponds to Co (OH) ₂ And further contains nickel element.

FIG. 5 is a transmission electron micrograph of the cobalt-nickel double hydroxide material prepared in this example, which shows that the prepared material is a film with significant wrinkles of about 100 to 200nm on the surface.

FIG. 9 is an atomic force microscope image of the cobalt vanadium double hydroxide nano-material prepared by the method, and the thickness analysis is about 4.5nm.

The preparation of the double-hydroxide self-assembled thin layer can be realized by adjusting the process parameters according to the content of the invention, and the performance basically consistent with the invention is shown. The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.

Claims

1. A preparation method of a double-hydroxide self-assembled thin-layer laminated structure assisted by oxygen is characterized by comprising the following steps:

step 1, weighing two transition metal salts, uniformly dispersing the two transition metal salts in deionized water containing saturated oxygen, and stirring and dissolving the two transition metal salts in an oxygen protective atmosphere to form a transparent solution; the transition metal salt is cobalt salt, nickel salt, vanadium salt and manganese salt, and the proportion of the two transition metal salts is (3-5): 1; in the step 1, continuously introducing oxygen into deionized water to form a saturated solution; the flow rate of oxygen is 70-100 mL/min, cobalt salts are cobalt nitrate, cobalt chloride and cobalt acetate, nickel salts are nickel nitrate, nickel chloride and nickel acetate, vanadium salts are vanadium chloride, and manganese salts are manganese nitrate and manganese acetate;

step 2, pouring alkali liquor into the transparent solution obtained in the step 1, keeping the saturated oxygen state of the liquid, and stirring in an oxygen protective atmosphere to obtain a precipitate; the stirring speed is 300-500 r/min, and the stirring time is 60-180 min; the alkali liquor is an aqueous solution of sodium hydroxide or potassium hydroxide, and the concentration is 2-5 mol/L; continuously introducing oxygen into the deionized water to form a saturated solution, wherein the flow of the oxygen is 100-150 mL/min;

2. The method for preparing a thin-layer layered structure self-assembled by an oxygen-assisted double hydroxide as claimed in claim 1, wherein the transition metal salt is used in an amount of 3 to 15mmol in step 1.

3. The method for preparing a double hydroxide self-assembled lamellar structure according to claim 1, characterized in that, in step 2, the stirring speed is 350-450 r/min and the stirring time is 100-150 min.

4. The method for preparing a thin-layer layered structure self-assembled by double hydroxide with oxygen assistance according to claim 1, wherein the vacuum drying temperature is 25-50 ℃ and the vacuum drying time is 10-20 h in step 3.

5. Use of the preparation method according to one of claims 1 to 4 for the preparation of a double hydroxide self-assembled film, characterized in that the double hydroxide self-assembled film has a two-dimensional structure with dimensions of 100 to 300nm and a thickness of less than 5nm.