CN111348676B - Porous metal oxide nanosheet and preparation method and application thereof - Google Patents
Porous metal oxide nanosheet and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a preparation method of porous two-dimensional metal oxide nanosheets, which realizes the purpose of pore forming by carrying out de-doping treatment on doped metal oxide nanosheets, and obtains a novel two-dimensional functional material with adjustable pore size and various metal oxide types. The preparation method comprises the steps of mixing a first metal oxide, an alkali metal salt and a second metal oxide, and preparing a layered composite material by solid-phase sintering; then protonating and stripping the layered composite material in sequence to obtain a doped metal oxide nanosheet; and then carrying out de-doping treatment on the obtained doped metal oxide nanosheet to realize pore forming, so as to obtain the porous two-dimensional metal oxide nanosheet. The method is a brand new way for preparing the ultrathin two-dimensional porous nano material, the aperture and the porosity of the prepared porous two-dimensional metal oxide nano sheet can be regulated and controlled, and the porous two-dimensional metal oxide nano sheet can be further prepared into powder and can be dispersed in a solution.
Description
Technical Field
The invention belongs to the technical field of nano materials, and particularly relates to a porous metal oxide nanosheet and a preparation method and application thereof.
Background
Takayoshi Sasaki and cooperative groups report preparation methods of various two-dimensional metal oxides, including preparation of a layered material from a single metal oxide and a multi-element metal oxide through a solid-heat sintering reaction, and preparation of a two-dimensional material by proton exchange and long-time shaking and stripping in a solution containing a surfactant. However, the Sasaki team rarely post-processes these two-dimensional nanomaterials to make porous or mesh two-dimensional materials. It has been reported that two-dimensional TiO has been formed by a high-temperature sintering method2Partial sintering shrinkage pore-forming of the nano sheet material, but pore size control is difficult through high-temperature sintering, only a porous aggregation structure is obtained, the nano sheet layer becomes thick and even collapses, and the shape is formedThe resulting sheet structure is not redispersible.
In addition to solid-phase sintering methods, there are other preparation methods, such as using graphene oxide template methods: mixing with a target metal oxide precursor, hydrolyzing, sintering, and finally removing graphene oxide in high-temperature oxygen. Depending on the degree of sintering, a two-dimensional material in the form of a mesh can be obtained. The porous material prepared by the method is formed by aggregating nano particles, has high thickness, is not tightly combined enough, is easy to collapse, and has large pore diameter reaching several nanometers or even more than ten nanometers.
The other method is a self-assembly method, which is to prepare ultra-small two-dimensional flaky metal oxide particles rich in edge defects, and self-assemble the particles in a freeze drying process under the action of a connecting agent to form a large-size ultra-thin flaky material.
There are also some methods for the preparation of two-dimensional materials which do not involve mesh modification, such as hydrothermal methods; ball milling; stripping the layered raw materials by utilizing the shearing force generated by the rapid flow of the mixed solution in the reactor and the continuous secondary flow formed at the bend to prepare the two-dimensional nano material; preparing a two-dimensional metal oxide by a liquid phase reaction; and preparing two-dimensional ultrathin materials by a bubble electrostatic spinning method, and the like.
From the above background, although many studies on two-dimensional metal oxide nanomaterials have been reported, the studies on two-dimensional mesh/porous nanomaterials and the preparation of porous materials by modifying them with two-dimensional materials are still in the initial stage. The modified/synthesized porous materials are mainly prepared by high-temperature sintering, nano-particle aggregation and other methods, and have the following problems: (1) the appearance is difficult to control; (2) the thickness of the two-dimensional material cannot be controlled at the atomic layer level, and the material utilization rate is low; (3) the prepared material has large thickness, high brittleness and poor film forming property; (4) the two-dimensional materials prepared cannot be redispersed in solution.
Disclosure of Invention
In order to solve the technical problem, the invention provides a preparation method of a porous two-dimensional metal oxide nanosheet, which comprises the following steps:
(1) mixing a first metal oxide, an alkali metal salt and a second metal oxide, and performing solid-phase sintering on the obtained mixture to obtain a layered composite material;
(2) protonating and stripping the layered composite material obtained in the step (1) in sequence to obtain a doped metal oxide nanosheet;
(3) and (3) carrying out de-doping treatment on the doped metal oxide nanosheet obtained in the step (2) to realize pore forming, so as to obtain the porous two-dimensional metal oxide nanosheet.
Optionally, redispersing the porous two-dimensional metal oxide nanosheet obtained in step (3) to obtain a solution of the porous two-dimensional metal oxide nanosheet, or drying to obtain the porous two-dimensional metal oxide nanosheet powder.
The first metal oxide and the second metal oxide are oxides of different metal elements, the first metal oxide is a main body in the doped metal oxide nanosheets, and the second metal oxide is a dopant in the doped metal oxide nanosheets. By "the first metal oxide is the host in the doped metal oxide nanosheets and the second metal oxide is the dopant in the doped metal oxide nanosheets", it is meant that the first metal oxide is the major constituent constituting the doped metal oxide nanosheets and the second metal oxide is the minor constituent constituting the doped metal oxide nanosheets. For example, in the doped metal oxide nanoplates, the weight of the first metal oxide: the weight of the second metal oxide is >1, preferably >1.5, preferably >2, preferably >3, preferably >4, preferably >5, preferably >10, preferably >20, preferably >50, preferably > 100.
According to an embodiment of the present invention, for example, the first metal oxide is an oxide of an alkaline earth metal and a transition metal, and may be one or more of oxides of elements such as calcium, barium, titanium, niobium, ruthenium, vanadium, tungsten, tantalum, hafnium, zirconium, chromium, molybdenum, manganese, lanthanum, cerium, praseodymium, neodymium, scandium, yttrium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and the like. For example, the second metal oxide is an oxide of a transition metal, and may be one or more of oxides of elements such as copper, iron, nickel, zinc, cobalt, palladium, niobium, ruthenium, vanadium, tungsten, tantalum, hafnium, zirconium, chromium, molybdenum, manganese, lanthanum, cerium, praseodymium, neodymium, scandium, yttrium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.
The first metal oxide is preferably one or more of titanium dioxide, niobium oxide, lanthanum oxide, tungsten oxide and vanadium oxide;
the second metal oxide is preferably one or more of copper oxide, iron oxide and nickel oxide.
According to an embodiment of the invention, the alkali metal salt in step (1) comprises one or more of a carbonate, nitrate, nitrite of an alkali metal; for example, it may be one or more of potassium carbonate, sodium carbonate, rubidium carbonate, cesium carbonate, lithium carbonate, potassium bicarbonate, sodium bicarbonate, rubidium bicarbonate, cesium bicarbonate, lithium nitrate, sodium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, lithium nitrite, sodium nitrite, potassium nitrite, rubidium nitrite, and cesium nitrite; further preferred is one or more of potassium carbonate and cesium carbonate.
According to an embodiment of the present invention, in the step (1), the first metal oxide, the alkali metal salt and the second metal oxide are mixed in a molar ratio of 1 (0.01 to 5) to (0.01 to 1), and the molar ratio is preferably 1 (0.05 to 1) to (0.01 to 0.5), and more preferably 1 (0.1 to 0.5) to (0.05 to 0.3).
According to an embodiment of the present invention, the molar ratio of the first metal oxide to the second metal oxide in step (1) determines the pore size and porosity in the porous two-dimensional metal oxide nanosheets, and the smaller the molar ratio, the larger the pore size in the resulting porous two-dimensional metal oxide nanosheets, the higher the porosity.
According to the embodiment of the present invention, the mixing in step (1) is physical mixing, which may be physical mixing means commonly used in the art, for example, dry mixing by a method such as grinding, or may be wet mixing followed by dry crushing and grinding into powder.
According to an embodiment of the present invention, the temperature of the solid phase sintering in step (1) is 500 to 2000 ℃, preferably 700 to 1500 ℃, and may be, for example, 1200 ℃;
the solid phase sintering time is 1-48 h, preferably 3-24 h, for example 6 h.
According to an embodiment of the present invention, the layered composite material obtained in step (1) has a lamellar structure, and the crystal lattice thereof contains the first metal oxide, the alkali metal ion in the alkali metal salt, and the second metal oxide.
According to an embodiment of the present invention, the step (2) includes the steps of:
(2a) protonation: stirring or soaking the layered composite material obtained in the step (1) in an acid solution to obtain a protonated layered material;
(2b) stripping: treating the protonated layered material obtained in the step (2a) by using a surfactant to realize stripping, so as to obtain the doped metal oxide nanosheet.
Optionally, the doped metal oxide nanoplates obtained from step (2b) may be further prepared as a solution or powder.
According to an embodiment of the present invention, the acid solution in step (2a) may be one or more of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, citric acid, acetic acid, perchloric acid, phosphoric acid; preferably one or more of hydrochloric acid, nitric acid and sulfuric acid;
the concentration of the acid solution is 0.01-20M, preferably 0.05-5M, for example, 0.5M, 1M;
the protonation temperature is 0-100 ℃, and preferably 25 ℃;
the stirring or soaking time can be 1-240 h, for example, 12 h;
the protonation may be repeated 1 to 10 times, for example, 2 times.
According to an embodiment of the present invention, after the stirring or soaking in step (2a) is finished, the protonated layered material is obtained through one or more steps of filtering, centrifuging, washing with water or drying.
According to the embodiment of the present invention, the surfactant in step (2b) may be one or more of alkylamine, alkylol amine, quaternary ammonium salt, quaternary ammonium base surfactant commonly used in the art, for example, one or more of triethanolamine, tetrabutylammonium hydroxide, ethanolamine, and diethanolamine;
the temperature of the stripping is 20 to 200 ℃, preferably 50 to 120 ℃, for example, 95 ℃;
the stripping treatment time is 0.1-240 h, preferably 6-24 h, for example, 16 h;
the stripping treatment mode can be one or more of stirring, hydrothermal treatment, oscillation treatment, ultrasonic treatment and microwave treatment.
According to the embodiment of the invention, after the stripping treatment in the step (2b) is finished, performing solid-liquid separation on the obtained mixture, and purifying to obtain the doped metal oxide nanosheet;
wherein the solid-liquid separation is any one of solid-liquid separation means commonly used in the art, and for example, the solid-liquid separation may be any one or more of centrifugation, filtration, standing and pouring of an upper layer solution;
the purification may be carried out by cleaning the solid obtained from the solid-liquid separation with a solvent, which is an inert solvent, which may be selected from any solvent which is inert under the reaction conditions, in particular does not react chemically with the starting materials and products, including for example one, a mixture of two or more selected from: alcohol solvents such as methanol, ethanol, isopropanol; ester solvents such as ethyl acetate or butyl acetate; hydrocarbon solvents such as benzene, toluene, xylene, hexane and cyclohexane; halogenated hydrocarbon solvents such as dichloromethane, trichloromethane, 1, 2-dichloroethane and chlorobenzene; or other solvents such as N, N-Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), acetonitrile, acetone, pyridine or water.
According to an embodiment of the present invention, the solvent is preferably one or more of water, methanol, ethanol, acetone, isopropanol.
According to an embodiment of the present invention, the doped metal oxide nanoplates obtained in step (2b) may be further prepared into a solution, comprising the steps of: adding the doped metal oxide nanosheets into a solvent for dispersion to obtain a solution of the doped metal oxide nanosheets.
The dispersing mode can be one or more of stirring, heating, solvothermal, hydrothermal, oscillation, ultrasonic and microwave;
the solution of doped metal oxide nanoplates has a solids content of 0% to 10%, such as 4.4%.
According to an embodiment of the present invention, the doped metal oxide nanosheets obtained in step (2b) may further be powdered, including the steps of: adding the doped metal oxide nanosheets into a solvent for dispersion to obtain a solution of the doped metal oxide nanosheets, and drying the solution of the doped metal oxide nanosheets to obtain powder of the doped metal oxide nanosheets.
Wherein the solvent, dispersion, has the definitions described above;
the drying may be any one of air drying, vacuum drying, oven drying, spray drying, and freeze drying.
According to an embodiment of the present invention, the dedoping method in the step (3) may be any one of acid treatment, extractant treatment, and reduction treatment.
As an example, when the doped metal oxide nanosheets obtained in step (2) are a powder, the dedoping may employ any one of acid treatment, extractant treatment, and reduction treatment;
as an example, when the doped metal oxide nanoplates obtained in step (2) are in solution, the dedoping may be treated with an acid or an extractant.
According to an embodiment of the invention, the acid treatment comprises the steps of: and reacting the doped metal oxide nanosheet with an acid-containing reagent, and performing post-treatment after the reaction is completed to obtain the porous two-dimensional metal oxide nanosheet.
According to an embodiment of the present invention, the acid-containing agent used in the acid treatment may include one or more of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, citric acid, acetic acid, perchloric acid, hypochlorous acid, phosphoric acid, peroxyacetic acid, thiosulfuric acid, ethylenediaminetetraacetic acid; preferably comprises one or more of nitric acid and hydrochloric acid;
the concentration of the acid in the acid-containing reagent is 0.01M to 10M, preferably 0.05M to 5M, and for example, may be 1M;
an additive can be added into the acid-containing reagent according to needs, and the additive can be an oxidizing agent.
According to the embodiment of the invention, the oxidant can be one or more of oxygen, sodium hypochlorite, potassium hypochlorite, hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate and potassium permanganate; preferably one or more of hydrogen peroxide and ammonium persulfate.
According to the embodiment of the invention, when the additive is gas, the additive is introduced in a bubbling mode, and the gas flow is 0.1-1000 standard milliliters per minute;
when the additive is a solid or liquid, the concentration of the solid or liquid additive is 0M to 10M (0M means no addition), preferably 0M to 5M, and may be, for example, 1M;
the molar ratio of the solid or liquid additive to the acid in the acid-containing reagent is 1 (1-50), preferably 1 (2-30), for example 1: 25.
The reaction temperature of the acid treatment is 0-100 ℃, and preferably 10-50 ℃;
the reaction mode of the acid treatment can be one or more of standing, stirring, ultrasonic, microwave, hydrothermal or oscillation;
the reaction time of the acid treatment can be 0.1-48 h, preferably 1-12 h, such as 3h and 4 h;
and (3) performing solid-liquid separation and then purifying solids after the acid treatment reaction is completed, wherein the solid-liquid separation and the purified solids are defined as in the step (2 b).
According to an embodiment of the invention, the extractant treatment comprises the following steps: and reacting the doped metal oxide nanosheet with an extracting agent, and performing post-treatment after complete reaction to obtain the porous two-dimensional metal oxide nanosheet.
According to the embodiment of the invention, the extractant used in the extractant treatment can be one or more of an ionic extractant, a coordination compound and an organic extractant which have extraction capacity on the second metal oxide;
the ion extracting agent can be one or more of ammonia water, potassium oxalate, sodium oxalate, potassium citrate, sodium citrate, ethylene diamine tetraacetic acid disodium salt, ethylene diamine tetraacetic acid tetrasodium salt, ethylene diamine tetraacetic acid dipotassium salt, ethylene diamine tetraacetic acid tetrapotassium salt, potassium thiocyanate, sodium thiocyanate, potassium cyanide, sodium sulfide, potassium sulfide, sodium thiosulfate and potassium thiosulfate;
the coordination compound can be one or more of P1, P50, Lix63, Lix64N, Lix65N, Lix70N, Lix984, P507, P204 and Cyanex 272;
the organic extracting agent can be one or more of crown ether compounds, alkyl carboxylic acids containing 3-30 carbon atoms and alkyl amines containing 3-30 carbon atoms.
According to the embodiment of the invention, the crown ether compound is preferably an organic substance containing 12-crown-4, 15-crown-5, 18-crown-6, dibenzo-18-crown-6 and dinitrogen-18-crown-6 in the molecule;
the alkyl carboxylic acid containing 3-30 carbon atoms is preferably a linear alkyl carboxylic acid containing 6-25 carbon atoms, and can be one or more of n-nonanoic acid, n-decanoic acid, n-undecanoic acid, n-dodecanoic acid, n-tridecanoic acid, n-tetradecanoic acid, n-pentadecanoic acid, n-hexadecanoic acid, n-heptadecanoic acid, n-octadecanoic acid, n-nonadecanoic acid, n-eicosanoic acid, n-heneicosanoic acid and n-docosanoic acid;
the alkylamine containing 3 to 30 carbon atoms is preferably straight-chain alkylamine containing 6 to 25 carbon atoms, and can be one or more of n-nonanamine, n-decylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-nonadecylamine, n-eicosylamine, n-heneicosylamine and n-docosylamine.
According to an embodiment of the invention, the extractant concentration may be between 0.01M and 10M, preferably between 0.05M and 5M, for example 1M.
According to the embodiment of the invention, the reaction temperature of the extractant treatment is 0-100 ℃, and preferably 10-50 ℃;
the reaction mode of the extraction agent treatment can be one or more of standing, stirring, ultrasound, microwave, hydrothermal treatment or oscillation;
the reaction time of the extractant treatment can be 0.1-48 h, preferably 1-12 h, such as 4 h;
the post-treatment of the extractant treatment is to perform solid-liquid separation and then purify the solid, and the definitions of the solid-liquid separation and the purification solid are the same as those in the step (2 b).
According to an embodiment of the invention, the reduction treatment comprises the steps of: sintering the doped metal oxide nanosheet sample in a reducing atmosphere, and then carrying out acid treatment to obtain the porous two-dimensional metal oxide nanosheet.
Wherein the acid treatment has the above-mentioned definition.
According to an embodiment of the present invention, the reducing atmosphere may be a reducing gas or a mixed gas thereof with an inert gas.
The reducing gas can be one or more of hydrogen, carbon monoxide, methane, ethane, ethylene, acetylene, ammonia gas, methanol, ethanol, silicomethane, diborane and the like;
the inert gas may be one or more of nitrogen, argon, helium.
The sintering temperature is 100 to 800 ℃, preferably 100 to 400 ℃, and for example, may be 200 ℃.
According to an embodiment of the present invention, the porous two-dimensional metal oxide nanosheets obtained in step (3) can be redispersed into a solution or powder, including the steps of: and (4) stripping the porous two-dimensional metal oxide nanosheet obtained in the step (3), and adding a solvent to prepare a porous two-dimensional metal oxide nanosheet solution, wherein the porous two-dimensional metal oxide nanosheet solution can be optionally dried to obtain the porous two-dimensional metal oxide nanosheet powder.
According to an embodiment of the present invention, the peeling and drying in the redispersion treatment have the above-mentioned definitions.
Further, the invention also provides a porous two-dimensional metal oxide nanosheet prepared according to the preparation method. The porous two-dimensional metal oxide nanosheet is of a porous two-dimensional nanosheet-shaped structure, and the size of the nanosheet is 10 nm-100 microns; the thickness of the sheet is 0.2 to 10nm, preferably 0.5 to 5nm, for example 1 to 2 nm; porosity is 0.1% to 80%, preferably 5% to 50%, and may be, for example, 8%, 19%, 25%, 34%; the pore diameter is 0.1-20 nm, preferably 0.5-5 nm, such as 0.5-1 nm, 0.5-2 nm, 1-3 nm, 1-5 nm.
The invention also provides application of the porous two-dimensional metal oxide nanosheet, which can be used in the fields of nanofiltration membrane modification, polymer modification, electrode materials, catalytic material load, functional membrane materials (permeable membranes and special materials), sensor materials, anticorrosive materials and the like.
The invention has the beneficial effects that:
(1) the purpose of controlling the pore size/porosity is achieved by controlling different doping degrees;
(2) the thickness of the obtained nano-sheet is from atom to several nanometers, and is thinner and larger than that of the nano-sheet prepared by a high-temperature sintering method in the prior art;
(3) the thickness of the layer is basically unchanged before and after the doping removal treatment of the nano-sheets, and the film forming property/flexibility is good;
(4) the prepared porous two-dimensional material can be redispersed in a solution through a surfactant or prepared into powder, and the application range is wide.
Drawings
FIG. 1 is anatase TiO2And the SEM of the layered composite material is obtained after solid-phase sintering of the potassium carbonate and the CuO.
FIG. 2 is an SEM of the protonated layered material from example 2.
FIG. 3 is a schematic representation of the reaction of triethanolAmine stripped resulting CuO doped TiO2XRD obtained by spin coating the nanosheet solution.
FIG. 4 shows CuO doped TiO obtained by triethanolamine stripping2SEM of powder samples obtained after freeze drying of the nanoplate solution.
FIG. 5 shows the CuO doped TiO resulting from triethanolamine stripping2Atomic Force Microscope (AFM) photographs of powder samples obtained after freeze-drying of the nanosheet solution revealed nanosheet thickness of 1.5nm and dimensions of hundreds of nm to several microns.
FIG. 6 shows CuO doped TiO obtained by triethanolamine stripping2Transmission electron micrographs of powder samples obtained after freeze drying of the nanosheet solution revealed dimensions ranging from hundreds of nm to several microns.
FIG. 7 shows CuO doped TiO obtained by triethanolamine stripping2The shape of the nano-sheet powder is SEM (scanning electron microscope) after reduction at 200 ℃ in hydrogen, and the particles on the surface of the nano-sheet are reduced Cu particles, so that a porous structure on the surface of the nano-sheet is left.
FIG. 8 shows the CuO-doped TiO obtained by triethanolamine stripping2Reducing nanosheet powder in hydrogen at 200 ℃, and removing precipitated Cu metal particles to obtain porous two-dimensional TiO2And (4) the appearance of a nano sheet SEM.
FIG. 9 is a CuO doped TiO2Nanosheet (TiO)21/0.14 (molar ratio))/CuO aqueous solution by treatment with 1M nitric acid to give porous two-dimensional TiO2The transmission electron microscope photo of the nanosheet aqueous solution shows that the size of the pores (white parts) is about 0.5-2 nm, and the porosity is about 19%.
FIG. 10 is a porous two-dimensional TiO compound2Porous two-dimensional TiO obtained by spray drying of nanosheet aqueous solution2SEM appearance of the nano-sheet powder sample.
Detailed Description
The preparation method of the present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
Example 1
After 40g of anatase titanium dioxide, 14g of potassium carbonate and 5.6g of copper oxide are ball-milled uniformly by a ball mill, the mixture is placed in a molybdenum crucible, sintered to 1200 ℃ at the heating rate of 10 ℃/min, kept for 6 hours and then cooled to room temperature, so that 54.8g of copper oxide doped layered composite material is obtained, and SEM test is carried out on the layered composite material, wherein the spectrum is shown in figure 1.
Example 2
To 50g of the solid obtained in example 1, 1L of a 0.5M hydrochloric acid solution was added, and after stirring at 25 ℃ for 12 hours, the solution was removed by filtration, and then the cake was added to 1L of a 0.5M hydrochloric acid solution and stirred at 25 ℃ for 12 hours. Filtered and washed thoroughly with water and dried. A CuO-doped protonated layered material 42g was obtained with an SEM image as shown in fig. 2.
Example 3
10g of the solid obtained in example 2, 50mL of a triethanolamine solution, and 500mL of water were mixed and stirred at 95 ℃ for 16 hours. And then cooling the system to room temperature, performing centrifugal separation to obtain a lower-layer solid, namely 15g (wet weight) of CuO-doped titanium dioxide nanosheet crude product, wherein the thickness of the lower-layer solid is 1.5nm, washing the lower-layer solid with water for 3 times, then adding 200mL of ethanol for ultrasonic dispersion to obtain a CuO-doped titanium dioxide nanosheet ethanol solution, and performing rotary coating on the solution to obtain a periodic XRD diffraction peak as shown in figure 3.
Example 4
Taking 10g of the solid obtained in the embodiment 2, obtaining 15g (wet weight) of CuO-doped titanium dioxide nanosheet crude product by the same operation as the embodiment 3, washing with water, purifying, and adding 200mL of water for ultrasonic dispersion to obtain 200mL of CuO-doped titanium dioxide nanosheet aqueous solution, wherein the nanosheet solid content is 4.4%.
Example 5
200mL of the CuO-doped titanium dioxide nanosheet aqueous solution obtained in the example 4 is taken to be prepared into a loose powder material through freeze drying, namely 8.8g of CuO-doped titanium dioxide nanosheet powder, wherein an SEM spectrum is shown in FIG. 4, an AFM spectrum is shown in FIG. 5, the thickness of the nanosheet is about 1.5nm, and a transmission electron microscope spectrum is shown in FIG. 6.
Example 6
2.0g of CuO-doped titanium dioxide nanosheet powder obtained in example 5 is treated at 200 ℃ for 2 hours in a hydrogen atmosphere to obtain porous titanium dioxide nanosheets precipitated from Cu nanoparticles, and an SEM spectrum of the porous titanium dioxide nanosheets is shown in FIG. 7. Stirring the porous titanium dioxide nanosheet separated from the Cu nanoparticles in a mixed solution of 50mL of 5M nitric acid solution and 10mL of 1M hydrogen peroxide at 50 ℃ for 3 hours, filtering and washing to obtain aggregated porous two-dimensional TiO2The SEM spectrum of the nanosheet solid is shown in FIG. 8, wherein the nanosheet solid is 1.6 g.
Example 7
Taking 50mL of the CuO-doped titanium dioxide nanosheet aqueous solution obtained in the step 4, dropwise adding 50mL of 1M nitric acid solution into the aqueous solution, stirring the solution at room temperature for 4 hours, standing the solution after the reaction is finished, filtering the solution, washing a filter cake with a large amount of water to obtain aggregated porous two-dimensional TiO21.9g of nanosheet solid, 50mL of water is added into the obtained solid for ultrasonic dispersion, and a photograph of a dispersed solution transmission electron microscope is shown in FIG. 9, wherein the size of the nanosheet is hundreds of nanometers to a few micrometers, the thickness of the nanosheet is 1.5nm, the pore diameter is 0.5-2 nm, and the porosity is about 19%.
Example 8
Taking 50mL of the CuO-doped titanium dioxide nanosheet aqueous solution obtained in the step 4, dropwise adding 50mL of 1M sodium citrate solution into the aqueous solution, stirring the solution at room temperature for 4 hours, standing the solution after the reaction is finished, filtering the solution, washing a filter cake with a large amount of water to obtain aggregated porous two-dimensional TiO22.0g of nanosheet solid.
Example 9
Porous two-dimensional TiO obtained in example 62Adding 0.5g of nanosheet solid into a mixed solution of 50mL of water and 5mL of triethanolamine, stirring for 16 hours at 95 ℃, cooling to room temperature, then carrying out centrifugal separation to obtain a lower-layer solid, washing for 3 times, adding 50mL of water, and carrying out ultrasonic dispersion to obtain the porous two-dimensional TiO2Aqueous solution of nanoplatelets.
Example 10
Porous two-dimensional TiO obtained in example 62Adding 0.5g of nanosheet solid into a mixed solution of 50mL of water and 5mL of triethanolamine, stirring for 16 hours at 95 ℃, cooling to room temperature, then carrying out centrifugal separation to obtain a lower-layer solid, washing for 3 times, adding 50mL of ethanol, and carrying out ultrasonic dispersion to obtain the porous two-dimensional TiO2Ethanol solution of nanosheet.
Example 11
Porous two-dimensional TiO obtained in EXAMPLE 9250mL of aqueous solution of the nanosheet is subjected to spray drying to obtain porous two-dimensional TiO20.27g of nanosheet powder. The SEM morphology is shown in FIG. 10.
Example 12
Three parts of anatase titanium dioxide, potassium carbonate and copper oxide are respectively weighed according to the proportion shown in table 1 to prepare three parts of mixtures, the mixtures are respectively placed in a molybdenum crucible after being ball-milled uniformly by a ball mill, the mixtures are sintered to 1200 ℃ at the heating rate of 10 ℃/min and are kept for 6 hours, and then the mixtures are cooled to room temperature, so that three copper oxide-doped layered composite materials are obtained, namely 52.7g, 56.0g and 59.1 g.
The three CuO-doped protonized layered materials are respectively added into 1L of 0.5M hydrochloric acid solution, stirred for 12 hours at 25 ℃, filtered to remove the solution, then the filter cake is added into 1L of 0.5M hydrochloric acid solution, stirred for 12 hours at 25 ℃, filtered, fully washed with water and dried to obtain 40.8g, 43.1g and 46.0g of three CuO-doped protonized layered materials.
10g of each CuO-doped protonated layered material is respectively mixed with 50mL of triethanolamine solution and 500mL of water, then stirred for 16 hours at 95 ℃, then the system is cooled to room temperature, centrifugal separation is carried out to obtain a lower-layer solid, and after the lower-layer solid is washed for 3 times, 500mL of water is added for ultrasonic dispersion to obtain 500mL of CuO-doped titanium dioxide nanosheet aqueous solution.
Respectively taking three portions of CuO-doped titanium dioxide nanosheet aqueous solution 50mL, dropwise adding 50mL of 1M nitric acid solution, stirring at room temperature for 4 hours, standing after the reaction is finished, filtering, washing a filter cake with a large amount of water to obtain three aggregation-state porous two-dimensional TiO22.9g of nanosheet solid, 3.3g andand 3.9g, adding 50mL of water into the obtained solid for ultrasonic dispersion, and performing transmission electron microscope test on the dispersed solution, wherein the pore diameter and porosity data are respectively shown in Table 1.
TABLE 1 different TiO2Pore diameter and porosity of porous nanosheet product obtained by CuO molar ratio
| Anatase titanium dioxide/g | Potassium carbonate/g | Copper oxide/g | TiO2Molar ratio of CuO to | Pore size/nm | Porosity of the | |
| Sample | ||||||
| 1 | 40 | 14 | 4 | 1/0.1 | 0.5～1 | 8 |
| Sample | ||||||
| 2 | 40 | 14 | 8 | 1/0.2 | 1～3 | 25 |
| Sample | ||||||
| 3 | 40 | 14 | 11.2 | 1/0.28 | 1～5 | 34％ |
It can be seen that the smaller the metal oxide host/dopant molar ratio, the higher the pore size and hence the porosity.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (13)
1. A preparation method of a porous two-dimensional metal oxide nanosheet comprises the following steps:
(1) mixing a first metal oxide, an alkali metal salt and a second metal oxide, and performing solid-phase sintering on the obtained mixture to obtain a layered composite material;
(2) protonating and stripping the layered composite material obtained in the step (1) in sequence to obtain a doped metal oxide nanosheet;
(3) performing de-doping treatment on the doped metal oxide nanosheet obtained in the step (2) to realize pore forming, so as to obtain the porous two-dimensional metal oxide nanosheet;
wherein the first metal oxide and the second metal oxide are oxides of different metal elements, the first metal oxide is a host in the doped metal oxide nanosheets, and the second metal oxide is a dopant in the doped metal oxide nanosheets;
the first metal oxide is an oxide of an alkaline earth metal and a transition metal;
the second metal oxide is an oxide of a transition metal;
the dedoping method in the step (3) is any one of acid treatment, extractant treatment and reduction treatment;
the acid treatment comprises the following steps: reacting the doped metal oxide nanosheet with an acid-containing reagent, and performing post-treatment after the reaction is completed to obtain a porous two-dimensional metal oxide nanosheet;
the extractant treatment comprises the following steps: reacting the doped metal oxide nanosheet with an extracting agent, and performing post-treatment after complete reaction to obtain the porous two-dimensional metal oxide nanosheet;
the reduction treatment comprises the following steps: sintering the doped metal oxide nanosheet sample in a reducing atmosphere, and then carrying out acid treatment to obtain the porous two-dimensional metal oxide nanosheet.
2. The production method according to claim 1, wherein the porous two-dimensional metal oxide nanosheet obtained in step (3) is redispersed to obtain a solution of the porous two-dimensional metal oxide nanosheet, or is dried to obtain a powder of the porous two-dimensional metal oxide nanosheet.
3. The method of claim 1, wherein the alkali metal salt comprises one or more of a carbonate, a nitrate, and a nitrite of an alkali metal.
4. The method according to claim 1, wherein the first metal oxide, the alkali metal salt and the second metal oxide are mixed in a molar ratio of 1 (0.01-5) to (0.01-1) in step (1).
5. The production method according to claim 1, wherein the layered composite material obtained in step (1) has a lamellar structure, and a crystal lattice thereof contains the first metal oxide, the alkali metal ion in the alkali metal salt, and the second metal oxide.
6. The method according to claim 1, wherein the step (2) comprises the steps of:
(2a) protonation: stirring or soaking the layered composite material obtained in the step (1) in an acid solution to obtain a protonated layered material;
(2b) stripping: treating the protonated layered material obtained in the step (2a) by using a surfactant to realize stripping, so as to obtain the doped metal oxide nanosheet.
7. The production method according to claim 6, wherein the doped metal oxide nanosheets obtained in step (2b) are further prepared as a solution or a powder.
8. The method of claim 1, wherein the acid-containing reagent comprises an additive.
9. The method of claim 8, wherein the additive is an oxidizing agent.
10. The preparation method according to claim 2, wherein the porous two-dimensional metal oxide nanosheets obtained in step (3) are redispersed into a solution or powder, comprising the steps of: and (4) stripping the porous two-dimensional metal oxide nanosheet obtained in the step (3), and adding the stripped porous two-dimensional metal oxide nanosheet into a solvent to prepare a porous two-dimensional metal oxide nanosheet solution.
11. The production method according to claim 10, wherein the porous two-dimensional metal oxide nanosheet solution is dried to obtain the porous two-dimensional metal oxide nanosheet powder.
12. The porous two-dimensional metal oxide nanosheet prepared by the preparation method of any one of claims 1 to 11, wherein the porous two-dimensional metal oxide nanosheet is a porous two-dimensional nanosheet-like structure having a size of 10nm to 100 μm, a sheet thickness of 0.2 to 10nm, a porosity of 0.1% to 80%, and a pore diameter of 0.1 to 20 nm.
13. The use of a porous two-dimensional metal oxide nanoplate as described in claim 12, wherein the porous two-dimensional metal oxide nanoplate is used in the field of nanofiltration membrane modification, polymer modification, electrode materials, catalytic material loading, functional membrane materials, sensor materials, and anti-corrosive materials.
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