A flaky porous nano-zinc oxide and a preparation method and application thereof

Abstract

The present application belongs to the technical field of nanometer material, and discloses a kind of sheet porous nanometer zinc oxide and its preparation method and application.The present application first prepares basic zinc carbonate precursor, then nitrogen is passed into, the pressure of system is >0.4MPa and <0.6MPa, hydrothermal reaction is carried out, and the reaction product is calcined, and sheet porous nanometer zinc oxide is prepared.The sheet porous nanometer zinc oxide prepared by the method of the present application has uniform and regular sheet porous structure, the holes on the sheet are uniform and regular, dense, small in particle size, large in specific surface area, and can be widely applied in the degradation of organic pollutants in photocatalytic system and the field of heavy metal adsorption.The preparation method of the present application can obtain raw materials easily and can be mass-produced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nanomaterials, and particularly relates to a sheet-shaped porous nanometer zinc oxide as well as a preparation method and application thereof. BACKGROUND

[0002] Nanometer zinc oxide is an important wide-bandgap semiconductor material, and the band gap at room temperature is 3.37 eV, and the electron beam binding capacity is 60 meV. Compared with traditional materials, nanometer zinc oxide exhibits more excellent electric, magnetic, optical, mechanical and chemical macro effects due to quantum size effect, surface effect and interface effect, so that it has broad application prospects in the fields of solar cells, gas sensitivity, photocatalysis and the like. The morphology and size of nanometer zinc oxide have great influence on its properties and application. In recent years, different structures of nanometer zinc oxide have been reported, such as nanofiber structure, nanobelt structure, urchin-like structure, dandelion-like structure and the like. The preparation methods of nanometer zinc oxide include sol-gel method, microemulsion method, self-assembly technology, vapor deposition method and the like. Núnez (Materials. Science in Semiconductor Processing, 2018, 81; 94-101) and the like pointed out that among several factors influencing the photocatalytic activity of semiconductor oxides, the most important ones are crystal structure, particle morphology, preferential orientation of crystal face and specific surface area.

[0003] Compared with other types of nanostructures, the porous structure has the advantages of large specific surface area, strong adsorption performance, adjustable pore structure and skeleton, and has excellent application prospects in the fields of catalysis, sensing, nano energy devices and the like. The porous nanometer zinc oxide can strengthen the absorption of incident light and the adsorption of molecules and ions, which is crucial to the performance improvement. However, the synthesis steps of the existing porous ZnO nanometer powder are complex, the cost is high, and it is difficult to mass-produce products with uniform morphology and particle size, and the size is still large, the particle size reaches 5-10 μm, and the thickness is nearly 1 μm, which cannot further improve the specific surface area.

[0004] Therefore, it is urgent to provide a sheet-shaped porous nanometer zinc oxide with smaller size, larger specific surface area and uniform morphology and particle size. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a sheet-shaped porous nanometer zinc oxide as well as a preparation method and application thereof. The sheet-shaped porous nanometer zinc oxide provided by the present application has small size, large specific surface area and uniform morphology and particle size, and can be better applied in a photocatalytic system to degrade organic pollutants.

[0006] The present application provides a preparation method of a sheet-shaped porous nanometer zinc oxide.

[0007] Specifically, the preparation method of the flaky porous nano zinc oxide comprises the following steps:

[0008] (1) preparing a basic zinc carbonate precursor;

[0009] (2) introducing nitrogen into the basic zinc carbonate precursor prepared in step (1) to make the pressure of the system > 0.4 MPa and < 0.6 MPa, and then performing a hydrothermal reaction to obtain a hydrothermal reaction product; and then calcining the hydrothermal reaction product to obtain the flaky porous nano zinc oxide.

[0010] The flaky porous nano zinc oxide prepared by the method has a uniform and regular morphology, a good monodispersity, a small particle size and a large specific surface area.

[0011] Preferably, the pressure of the system in step (2) is 0.45-0.58 MPa.

[0012] Further preferably, the pressure of the system in step (2) is 0.5-0.55 MPa.

[0013] Preferably, the basic zinc carbonate precursor in step (1) is prepared by using sodium carbonate, zinc sulfate and a surfactant as main raw materials and by using a multiphase interface reactor.

[0014] Preferably, the temperature for the reaction of the multiphase interface reactor is 5-40℃, and the pressure is normal pressure.

[0015] Preferably, the pH value is controlled to be 9-10 during the reaction of the multiphase interface reactor.

[0016] Preferably, the sodium carbonate is prepared into a sodium carbonate solution before the reaction, and the concentration of the sodium carbonate solution is 0.5-3 mol / L.

[0017] Further preferably, the concentration of the sodium carbonate solution is 0.5-2.13 mol / L.

[0018] Preferably, the zinc sulfate is prepared into a zinc sulfate solution before the reaction, and the concentration of the zinc sulfate solution is 0.10-1.00 mol / L.

[0019] Further preferably, the concentration of the zinc sulfate solution is 0.19-0.79 mol / L.

[0020] Preferably, the surfactant comprises at least one of sodium oleate, polyethylene glycol, and polyvinylpyrrolidone.

[0021] Preferably, before the reaction, the surfactant is prepared into a surfactant solution, which comprises at least one of a sodium oleate solution, a polyethylene glycol solution, and a polyvinylpyrrolidone solution.

[0022] Preferably, the concentration of the sodium oleate solution is 0.003-0.01 mol / L.

[0023] Further preferably, the concentration of the sodium oleate solution is 0.00395-0.0079 mol / L.

[0024] Preferably, the polyethylene glycol solution is 1.2-7 g / L.

[0025] Further preferably, the polyethylene glycol solution is 1.48-6.32 g / L.

[0026] Preferably, in step (2), the temperature of the hydrothermal reaction is 150-220 °C, and the time of the hydrothermal reaction is 8-12 hours.

[0027] Preferably, in step (2), the pressure of the system during the hydrothermal reaction is 1.2-2.0 Mpa.

[0028] Preferably, in step (2), the hydrothermal reaction is stirred at a speed of 200-500 r / min.

[0029] Preferably, in step (2), the temperature of the calcination is 400-600 °C, and the time of the calcination is 0.5-2 hours.

[0030] Preferably, in step (2), the hydrothermal reaction product is washed and dried before calcination.

[0031] Preferably, the washing process comprises washing with pure water and then washing with alcohol.

[0032] Preferably, the drying process comprises drying at 60-80 °C for 12-48 hours.

[0033] Preferably, the method for preparing the flaky porous nano zinc oxide comprises the following steps:

[0034] (1) dissolving sodium carbonate in water to prepare a sodium carbonate solution with a concentration of 0.5-25 mol / L; dissolving zinc sulfate to prepare a zinc sulfate solution with a concentration of 0.10-1.00 mol / L, and adding polyethylene glycol to make the concentration of polyethylene glycol 1.2-7.00 g / L; dissolving sodium oleate in water to prepare a sodium oleate solution with a concentration of 0.003-0.01 mol / L;

[0035] (2) carrying out co-current precipitation reaction of the sodium carbonate solution, the zinc sulfate solution and the sodium oleate solution obtained in step (1) through a multiphase interface reactor, wherein the reaction is carried out at room temperature, the stirring speed is controlled to be 2000-4000 r / min, and the pH value is controlled to be 9-10, to prepare a basic zinc carbonate precursor;

[0036] (3) adding the basic zinc carbonate precursor obtained in step (2) into a high-pressure hydrothermal kettle, introducing nitrogen to make the pressure of the system 0.42-0.58 MPa, and then heating to 150-220 ℃ for hydrothermal reaction for 8-12 hours, wherein the pressure in the kettle during the reaction is 1.2-2.0 MPa; during the hydrothermal reaction, stirring is carried out, and the stirring speed is 200-500 r / min; after the reaction is completed, the temperature is lowered to room temperature, the pressure in the kettle returns to 0.42-0.58 MPa, and white slurry is obtained;

[0037] (4) washing and drying the white slurry obtained in step (3) to obtain a basic zinc carbonate precursor;

[0038] (5) calcining the basic zinc carbonate precursor obtained in step (4) at 400-600 ℃ for 0.5-2 hours to obtain porous nano zinc oxide.

[0039] The second aspect of the present application provides a sheet-shaped porous nano zinc oxide.

[0040] The sheet-shaped porous nano zinc oxide prepared by the above preparation method has a specific surface area of 60-70 m 2 / g, and / or a particle size of 50-200 nm, and / or a thickness of 5-15 nm, and / or a pore size of 8-20 nm.

[0041] Further preferably, the sheet-shaped porous nano zinc oxide has a specific surface area of 65.158-65.515 m 2 / g, and / or a particle size of 80-170 nm, and / or a thickness of 8-10 nm, and / or a pore size of 10-18 nm.

[0042] The third aspect of the present application provides an application of the sheet-shaped porous nano zinc oxide.

[0043] The application of a sheet-shaped porous nanometer zinc oxide in the field of photocatalysis, heavy metal adsorption or organic pollutant degradation.

[0044] The application of a sheet-shaped porous nanometer zinc oxide in the field of degradation of organic pollutants by using a photocatalytic system.

[0045] Preferably, the organic pollutants include, but are not limited to, at least one of methyl orange, p-chlorophenol, and antibiotics.

[0046] Compared with the prior art, the application has the following beneficial effects:

[0047] The sheet-shaped porous nanometer zinc oxide is prepared by first preparing a basic zinc carbonate precursor, then introducing nitrogen into the basic zinc carbonate precursor to perform a hydrothermal reaction, controlling the amount of nitrogen introduced to control the morphology of the material, and then calcining the hydrothermal reaction product. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 The XRD spectrum of the sheet-shaped porous nanometer zinc oxide prepared in Example 1;

[0049] Figure 2 The SEM image of the basic zinc carbonate precursor prepared in Example 1;

[0050] Figure 3 The SEM image of the sheet-shaped porous nanometer zinc oxide prepared in Example 1 under a scale of 100 nm;

[0051] Figure 4 The SEM image of the sheet-shaped porous nanometer zinc oxide prepared in Example 1 under a scale of 200 nm;

[0052] Figure 5 The SEM image of the nanometer zinc oxide prepared in Comparative Example 1 under a scale of 200 nm;

[0053] Figure 6 The SEM image of the nanometer zinc oxide prepared in Comparative Example 2 under a scale of 200 nm;

[0054] Figure 7 The SEM image of the zinc oxide prepared in Comparative Example 3 under a scale of 20 μm. DETAILED DESCRIPTION

[0055] In order to make the skilled in the art more clearly understand the technical solutions described in the present application, the following examples are listed for illustration. It should be noted that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0056] The raw materials, reagents or devices used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0057] Example 1

[0058] A method for preparing a sheet-shaped porous nano zinc oxide, comprising the following steps:

[0059] (1) Dissolve sodium carbonate raw material in water to prepare a 2.13M sodium carbonate solution; prepare a 0.79M zinc sulfate solution by dissolving zinc sulfate raw material, and add polyethylene glycol to make its concentration 6.32g / L; dissolve sodium oleate raw material in water to prepare a 0.0079M sodium oleate solution;

[0060] (2) Perform co-current precipitation reaction on the three solutions obtained in step (1) through a multiphase interface reactor, with stirring speed of 3000r / min, reaction pH value of 9-10, and reaction at room temperature, to prepare an alkali zinc carbonate precursor slurry;

[0061] (3) Put the alkali zinc carbonate precursor slurry obtained in step (2) into a 500mL high-pressure hydrothermal kettle, and introduce N2 gas to make the initial pressure in the hydrothermal kettle 0.5MPa; then heat to 180℃ for hydrothermal reaction for 10 hours, with the pressure in the kettle being 1.55MPa during the reaction; after the reaction, naturally cool to room temperature, and the pressure in the kettle returns to 0.5MPa, to obtain a white slurry;

[0062] (4) Wash and dry the white slurry obtained in step (3) to obtain an alkali zinc carbonate precursor solid; the morphology of the alkali zinc carbonate precursor is shown in Figure 2 It can be seen from Figure 2 that the uncalcined alkali zinc carbonate precursor has no porous structure.

[0063] (5) Calcine the alkali zinc carbonate precursor solid obtained in step (4) at 400℃ for 1 hour to obtain sheet-shaped porous nano zinc oxide.

[0064] The XRD spectrum of the sheet-shaped porous nano zinc oxide prepared in Example 1 is shown in Figure 1 It can be seen from Figure 1 that the crystal structure of the sheet-shaped porous nano zinc oxide is hexagonal wurtzite structure, with good crystallinity and high purity. The SEM image of the sheet-shaped porous nano zinc oxide is shown in Figure 3 , Figure 4As shown in the figure, the flaky porous nanometer zinc oxide is in a regular transparent flaky shape, and has uniform and regular and dense holes on the flaky structure and does not contain zinc oxide of other morphologies. Figure 1 Intensity is intensity.

[0065] Example 2

[0066] A preparation method of flaky porous nanometer zinc oxide comprises the following steps:

[0067] (1) Dissolve sodium carbonate raw material in water to prepare a 2.13M sodium carbonate solution; prepare a 0.79M zinc sulfate solution from zinc sulfate raw material, and add polyethylene glycol to make the concentration of polyethylene glycol be 6.32g / L; dissolve sodium oleate raw material in water to prepare a 0.0079M sodium oleate solution;

[0068] (2) Perform concurrent precipitation reaction on the three solutions obtained in step (1) through a multiphase interface reactor, the stirring speed is 3000r / min, the reaction pH value is 9-10, and the reaction is performed at room temperature to prepare an alkali carbonate zinc precursor slurry;

[0069] (3) Put the alkali carbonate zinc precursor slurry obtained in step (2) into a 500mL high-pressure hydrothermal kettle, introduce N2 gas to make the initial pressure in the hydrothermal kettle be 0.5MPa, then heat to 220℃ and hydrothermally react for 8 hours, the pressure in the kettle during the reaction is 1.65MPa, after the reaction, naturally cool to room temperature, the pressure in the kettle returns to 0.5MPa, and a white slurry is obtained;

[0070] (4) Wash and dry the white slurry obtained in step (3) to obtain alkali carbonate zinc precursor solid;

[0071] (5) Calcine the alkali carbonate zinc precursor solid obtained in step (4) at 400℃ for 1 hour to obtain porous nanometer zinc oxide powder.

[0072] Perform morphology analysis on the prepared nanometer zinc oxide, and the structure is basically consistent with the product prepared in example 1.

[0073] Example 3

[0074] A preparation method of flaky porous nanometer zinc oxide comprises the following steps:

[0075] (1) Dissolve sodium carbonate raw material in water to prepare a 2.13M sodium carbonate solution; prepare a 0.79M zinc sulfate solution from zinc sulfate raw material, and add polyethylene glycol to make the concentration of polyethylene glycol be 6.32g / L; dissolve sodium oleate raw material in water to prepare a 0.0079M sodium oleate solution;

[0076] (2) The three solutions obtained in step (1) are subjected to a parallel flow precipitation reaction through a multiphase interface reactor, the stirring speed is 3000 r / min, the reaction pH value is 9-10, and the reaction is carried out at room temperature to obtain a basic zinc carbonate precursor slurry;

[0077] (3) The basic zinc carbonate precursor slurry obtained in step (2) is added to a 500 mL high-pressure hydrothermal kettle, N2 gas is introduced to make the initial pressure in the hydrothermal kettle 0.5 MPa. Heating to 150°C hydrothermal reaction for 12 hours, the pressure in the kettle during the reaction is 1.45 MPa; after the reaction is completed, it is naturally cooled to room temperature, the pressure in the kettle returns to 0.5 MPa, and a white slurry is obtained;

[0078] (4) The white slurry obtained in step (3) is washed and dried to obtain a basic zinc carbonate precursor solid;

[0079] (5) The basic zinc carbonate precursor solid obtained in step (4) is calcined at 400°C for 1 hour to obtain porous nano zinc oxide powder.

[0080] The prepared nano zinc oxide is subjected to morphology analysis, and the structure is basically consistent with the product prepared in Example 1.

[0081] Example 4

[0082] A method for preparing flaky porous nano zinc oxide, comprising the following steps:

[0083] (1) Sodium carbonate raw material is dissolved in water to prepare a 2.13M sodium carbonate solution; zinc sulfate raw material is prepared into a 0.79M zinc sulfate solution, and polyethylene glycol is added to make the concentration 6.32g / L; sodium oleate raw material is dissolved in water to prepare a 0.0079M sodium oleate solution;

[0084] (2) The three solutions obtained in step (1) are subjected to a parallel flow precipitation reaction through a multiphase interface reactor, the stirring speed is 3000 r / min, the reaction pH value is 9-10, and the reaction is carried out at room temperature to obtain a basic zinc carbonate precursor slurry;

[0085] (3) The basic zinc carbonate precursor slurry obtained in step (2) is added to a 500 mL high-pressure hydrothermal kettle, N2 gas is introduced to make the initial pressure in the hydrothermal kettle 0.55 MPa. Then heated to 180°C hydrothermal reaction for 10 hours, the pressure in the kettle during the reaction is 1.60 MPa. After the reaction is completed, it is naturally cooled to room temperature, the pressure in the kettle returns to 0.5 MPa, and a white slurry is obtained;

[0086] (4) The white slurry obtained in step (3) is washed and dried to obtain a basic zinc carbonate precursor solid;

[0087] (5) The basic zinc carbonate precursor solid obtained in step (4) is calcined at 400°C for 1 hour to obtain flaky porous nano zinc oxide.

[0088] The prepared nano zinc oxide is subjected to morphology analysis, and the structure is basically consistent with the product prepared in Example 1.

[0089] Comparative Example 1

[0090] A method for preparing nano zinc oxide, which is different from Example 1 in that the N2 introduced in step (3) is adjusted to make the initial pressure in the hydrothermal kettle 0.4 MPa.

[0091] The prepared nano zinc oxide is further subjected to morphology analysis, Figure 5 which is the SEM image of the nano zinc oxide. As can be seen from Figure 5 when the initial pressure is 0.4 MPa, the nitrogen gas is not enough, and the nitrogen gas has a small regulating effect on the morphology of the zinc oxide. The zinc oxide is irregularly flaky, has poor uniformity, part of the size is large, and has aggregation and adhesion phenomenon; and has no pore structure, which cannot improve the specific surface area of the zinc oxide.

[0092] Comparative Example 2

[0093] A method for preparing nano zinc oxide, which is different from Example 1 in that the N2 introduced in step (3) is adjusted to make the initial pressure in the hydrothermal kettle 0.6 MPa.

[0094] The prepared nano zinc oxide is subjected to morphology analysis, Figure 6 which is the SEM image of the nano zinc oxide. As can be seen from Figure 6 when the nitrogen gas is excessive and the initial pressure is as high as 0.6 MPa, the nitrogen gas has an excessive regulating effect on the morphology of the zinc oxide. The flaky zinc oxide is curled, and the particles are obviously shed, which cannot prepare flaky porous nano zinc oxide with uniform and dense pores and stable structure.

[0095] Comparative Example 3

[0096] A method for preparing zinc oxide, which is different from Example 1 in that no N2 gas is introduced in step (3).

[0097] The prepared zinc oxide is subjected to morphology analysis, Figure 7 which is the SEM image of the zinc oxide. As can be seen from Figure 7 the prepared product contains micron-level needle-like structure and micron-level granular structure, and has large size and poor morphology uniformity, and has small specific surface area.

[0098] Product effect test

[0099] The purity and specific surface area of the zinc oxide products prepared in each example and comparative example are tested. The test results are shown in Table 1.

[0100] Table 1

[0101]

[0102] As shown in Table 1, the flaky porous nano zinc oxide provided by the embodiments 1-4 has high purity, small particle size, thin thickness, large specific surface area, low degree of particle agglomeration, and uniform morphology and particle size. In the hydrothermal reaction process of Comparative Example 1, the initial pressure in the hydrothermal kettle is reduced, nitrogen is insufficient, and the control effect on the morphology of zinc oxide is small, resulting in irregular flaky zinc oxide, poor uniformity, serious agglomeration and adhesion of part of the zinc oxide, and no pore structure, which cannot improve the specific surface area of zinc oxide.

[0103] In the hydrothermal reaction process of Comparative Example 2, the initial pressure in the hydrothermal kettle is increased, and nitrogen is excessively controlled to the morphology of zinc oxide, resulting in curling of the flaky zinc oxide, and obvious particle shedding.

[0104] In the hydrothermal reaction process of Comparative Example 3, no N2 is introduced, and the product obtained is micron grade, large size, poor morphology uniformity, and small specific surface area.

Claims

1. A method for preparing sheet-like porous nano-zinc oxide, characterized in that, Includes the following steps: (1) Preparation of basic zinc carbonate precursor; (2) Nitrogen gas is introduced into the basic zinc carbonate precursor prepared in step (1) so that the initial pressure of the system is >0.4MPa and <0.6MPa, and then a hydrothermal reaction is carried out to obtain the hydrothermal reaction product; then the hydrothermal reaction product is calcined to obtain the sheet-like porous nano zinc oxide. In step (2), the temperature of the hydrothermal reaction is 150-220℃, and the time of the hydrothermal reaction is 8-12 hours.

2. The preparation method according to claim 1, characterized in that, In step (2), the pressure of the system is made to reach 0.45-0.58 MPa.

3. The preparation method according to claim 1, characterized in that, In step (1), the basic zinc carbonate precursor is prepared by reacting sodium carbonate, zinc sulfate and surfactant as the main raw materials in a multiphase interface reactor.

4. The preparation method according to claim 3, characterized in that, The reaction temperature using a multiphase interface reactor is 5-40℃, and the pressure is atmospheric pressure.

5. The preparation method according to claim 3, characterized in that, The surfactant includes at least one of sodium oleate, polyethylene glycol, and polyvinylpyrrolidone.

6. The preparation method according to claim 1, characterized in that, In step (2), the roasting temperature is 400-600℃ and the roasting time is 0.5-2 hours.

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