CN111229316A - Preparation method of zinc oxide supported three-dimensional honeycomb carbon-based nano material with adjustable aperture - Google Patents

Preparation method of zinc oxide supported three-dimensional honeycomb carbon-based nano material with adjustable aperture Download PDF

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CN111229316A
CN111229316A CN202010152658.XA CN202010152658A CN111229316A CN 111229316 A CN111229316 A CN 111229316A CN 202010152658 A CN202010152658 A CN 202010152658A CN 111229316 A CN111229316 A CN 111229316A
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zinc oxide
polyvinyl alcohol
dimensional honeycomb
honeycomb carbon
nano material
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CN111229316B (en
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沈意
沈义新
朱超
宋爽
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Zhejiang University of Technology ZJUT
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/06Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing polymers
    • B01J31/069Hybrid organic-inorganic polymers, e.g. silica derivatized with organic groups
    • B01J35/56
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/30Treatment of water, waste water, or sewage by irradiation
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00Nature of the contaminant
    • C02F2101/30Organic compounds
    • C02F2101/38Organic compounds containing nitrogen
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2305/00Use of specific compounds during water treatment
    • C02F2305/10Photocatalysts

Abstract

The invention discloses a preparation method of a three-dimensional honeycomb carbon-based nano material with adjustable zinc oxide loading aperture, which is constructed by adopting an ice template assembly method, and graphene oxide, polyvinyl alcohol and zinc oxide are used as raw materials to prepare uniform hydrogel; and (3) solidifying the hydrogel on the ice template by a vacuum freeze drying technology, and then removing the ice template to form the three-dimensional honeycomb carbon-based nano material. The invention can accurately regulate and control the aperture of the three-dimensional honeycomb carbon-based nano material by changing the molecular weight of polyvinyl alcohol, the zinc oxide loaded on the three-dimensional honeycomb carbon-based nano material has no agglomeration and high dispersion degree, the absorption and utilization rate of light are improved, the photocatalytic performance of the zinc oxide is greatly enhanced, and the invention can be used in the field of wastewater treatment. The three-dimensional honeycomb carbon-based nano material prepared by the method has good mechanical strength, can be recycled and has good industrial application prospect.

Description

Preparation method of zinc oxide supported three-dimensional honeycomb carbon-based nano material with adjustable aperture
Technical Field
The invention belongs to the field of material preparation, and particularly relates to a preparation method of a three-dimensional honeycomb carbon-based nano material with adjustable zinc oxide loading aperture.
Background
Graphene oxide is a compound formed by sp from carbon atoms2The hybridized two-dimensional periodic honeycomb carbon-based nano material has an ultra-large theoretical specific surface area (2630 m)2g-1) Can be used as a high-adsorption material. The graphene oxide is constructed into the three-dimensional honeycomb carbon-based nano material with the porous structure, so that the application field of the material can be further widened. The pore size of the three-dimensional honeycomb carbon-based nano material determines the specific surface area and the number of adsorption sites, and the adsorption performance of the material is greatly influenced. However, the existing preparation method of the three-dimensional honeycomb carbon-based nano material has the defects that the aperture of the three-dimensional honeycomb carbon-based nano material cannot be accurately controlled, so that the improvement of the adsorption performance of the three-dimensional honeycomb carbon-based nano material is limited. For example, chinese patent CN201510364275.8 discloses a three-dimensional honeycomb carbon-based nanomaterial self-assembled by hydrothermal method, but cannot prepare porous structure with adjustable pore size; chinese patent CN201610809438.3 discloses a three-dimensional honeycomb carbon-based nano material prepared by a chemical deposition method, however, the morphology of graphene is limited by the morphology of a deposition matrix, thereby limiting the popularization and application of the method. Meanwhile, due to the ultralow density and the porous structure, the three-dimensional honeycomb carbon-based nano material has poor mechanical properties, and cannot be reused in industry for many times.
Zinc oxide is an important semiconductor material, has the energy band width of 3.37eV and strong electronic excitation energy of 60meV, and can degrade organic substances under ultraviolet light. However, since graphene oxide has rich oxygen-containing functional groups, zinc oxide is difficult to directly load on graphene oxide and is easy to fall off, and if a method for reducing graphene is adopted, zinc oxide is reduced and the photocatalytic performance is lost. Therefore, the preparation method of the three-dimensional honeycomb carbon-based nano material with adjustable zinc oxide load aperture is very important to find.
Disclosure of Invention
Aiming at the technical problems, the invention provides a preparation method of a three-dimensional honeycomb carbon-based nano material with adjustable zinc oxide load aperture, which uses a cross-linking agent polyvinyl alcohol (PVA) to connect graphene sheets, regulates and controls the aperture of the three-dimensional honeycomb carbon-based nano material by changing the molecular weight of the PVA, and the aperture ranges from micropores, mesopores to macropores; the polyvinyl alcohol with a linear structure can also be used as a support of a porous structure of the three-dimensional honeycomb carbon-based nano material, so that the mechanical strength of the three-dimensional honeycomb carbon-based nano material is enhanced; under the condition of adding polyvinyl alcohol, a large amount of zinc oxide can be loaded on the graphene sheet.
The preparation method of the three-dimensional honeycomb carbon-based nano material with adjustable zinc oxide loading aperture is characterized by comprising the following steps:
1) adding graphene oxide into water, and uniformly dispersing by using ultrasonic waves to obtain a graphene oxide suspension;
2) adding zinc oxide into the graphene oxide suspension obtained in the step 1), and uniformly mixing by ultrasonic to obtain a zinc oxide-graphene oxide dispersion liquid;
3) adding polyvinyl alcohol into deionized water, heating, stirring and dissolving to obtain a polyvinyl alcohol aqueous solution; mixing the polyvinyl alcohol aqueous solution with the zinc oxide-graphene oxide dispersion liquid obtained in the step 2), and performing ultrasonic treatment for 0.5-2 hours to obtain a polyvinyl alcohol-zinc oxide-graphene oxide aqueous solution;
4) and (3) putting the polyvinyl alcohol-zinc oxide-graphene oxide aqueous solution obtained in the step (3) into a cylindrical freezing pipe by adopting an ice template assembly method, freezing at a low temperature, forming hydrogel by the polyvinyl alcohol-zinc oxide-graphene oxide aqueous solution under the action of the low temperature, and putting the hydrogel into a vacuum freeze dryer for drying treatment when the internal temperature of the hydrogel is consistent with the freezing temperature and does not change any more and the liquid water in the hydrogel is completely changed into ice, so as to obtain the cylindrical three-dimensional honeycomb carbon-based nano material with the porous structure.
The preparation method of the three-dimensional honeycomb carbon-based nanomaterial with the adjustable zinc oxide loading aperture is characterized in that in the step 1), the size of a sheet layer of the graphene oxide is larger than 30 um, and the concentration of the prepared graphene oxide suspension is 2-6 mg/L, preferably 3-4 mg/L.
The preparation method of the three-dimensional honeycomb carbon-based nanomaterial with the adjustable zinc oxide loading aperture is characterized in that in the step 2), the particle size of zinc oxide is 10-30 nm, and the mass ratio of zinc oxide to graphene oxide in a graphene oxide suspension is 1: 5-1: 10, preferably 1: 7-1: 8.
The preparation method of the three-dimensional honeycomb carbon-based nano material with the adjustable zinc oxide load aperture is characterized in that in the polyvinyl alcohol aqueous solution obtained in the step 3), the mass ratio of polyvinyl alcohol to deionized water is 6-12: 100, and preferably 9-10: 100; and 3) mixing the polyvinyl alcohol aqueous solution with the zinc oxide-graphene oxide dispersion liquid, wherein the mass ratio of the polyvinyl alcohol to the graphene oxide is 20-30: 1.
The preparation method of the three-dimensional honeycomb carbon-based nano material with the adjustable zinc oxide load aperture is characterized in that in the step 1), the step 2) or the step 3), the ambient temperature in the ultrasonic process is room temperature, the ultrasonic frequency is 30-50 KHz, and the ultrasonic power is 200-300W.
The preparation method of the three-dimensional honeycomb carbon-based nanomaterial with the adjustable zinc oxide loading aperture is characterized in that in the step 4), the low-temperature freezing time is 10-15 hours, and the low-temperature freezing temperature is-80 ℃ to-70 ℃; the drying time is 40-50 h, and the drying temperature is-30 ℃ to-20 ℃.
The preparation method of the three-dimensional honeycomb carbon-based nano material with the adjustable zinc oxide loading pore diameter is characterized in that the molecular weight of polyvinyl alcohol is 5000-60000, and preferably 20000-25000. The microporous three-dimensional honeycomb carbon-based nano material can be obtained under the condition that the polyvinyl alcohol has low molecular weight (5000-10000), and the aperture range of the microporous three-dimensional honeycomb carbon-based nano material is 40-60 mu m. According to the invention, the mesoporous three-dimensional honeycomb carbon-based nano material can be obtained under the condition that polyvinyl alcohol is medium molecular weight (20000-25000), and the pore diameter range of the mesoporous three-dimensional honeycomb carbon-based nano material is 100-120 um. According to the invention, the macroporous three-dimensional honeycomb carbon-based nano material can be obtained under the condition that polyvinyl alcohol has high molecular weight (50000-60000), and the aperture range of the material is 280-300 mu m.
The beneficial effects obtained by the invention are as follows:
1) the invention provides a preparation method of a three-dimensional honeycomb carbon-based nano material with adjustable zinc oxide loading aperture, the three-dimensional honeycomb carbon-based nano material is constructed by adopting an ice template assembly method, and Graphene Oxide (GO), polyvinyl alcohol (PVA) and zinc oxide (ZnO) are used as raw materials to prepare uniform graphene hydrogel; and (3) solidifying the graphene on the ice template by using a vacuum freeze drying technology, and then removing the ice template to form the three-dimensional honeycomb carbon-based nano material. The cross-linking agent polyvinyl alcohol is used for connecting the graphene sheets, the pore diameter of the three-dimensional honeycomb carbon-based nano material is regulated and controlled by changing the molecular weight of the polyvinyl alcohol, the polyvinyl alcohol with a linear structure can be used as a support of the three-dimensional honeycomb carbon-based nano material with a porous structure, and meanwhile, a large amount of zinc oxide can be loaded on the three-dimensional honeycomb carbon-based nano material. The zinc oxide loaded on the three-dimensional honeycomb carbon-based nano material has no agglomeration and high dispersion degree, improves the absorption and utilization rate of light, greatly enhances the photocatalytic performance of the zinc oxide, and can be used in the field of catalysis.
2) The three-dimensional cellular carbon-based nano material with the mesoporous structure prepared by the invention has extremely high photocatalytic conversion rate to nitrobenzene. When different organic pollutants are degraded, three-dimensional honeycomb carbon-based nano materials with different pore sizes may be needed as catalysts to perform photocatalytic reaction. The method can properly change the molecular weight of the polyvinyl alcohol, and further adjust the aperture of the three-dimensional honeycomb carbon-based nano material, so that the degradation treatment of the organic pollutants can be carried out under the optimal catalytic condition. The three-dimensional honeycomb carbon-based nano material prepared by the method has extremely strong absorption photocatalysis performance and mechanical strength.
Drawings
FIG. 1a is an electron microscope scanning image of the microporous three-dimensional honeycomb carbon-based nanomaterial prepared under the condition of low molecular weight (5000-10000) polyvinyl alcohol in example 1;
FIG. 1b is an electron microscope scanning image of the three-dimensional honeycomb carbon-based nanomaterial loaded with Zn element in example 1;
FIG. 2a is an electron microscope scanning image of the mesoporous three-dimensional honeycomb carbon-based nanomaterial prepared under the condition of polyvinyl alcohol with a medium molecular weight (20000-25000) in example 3;
FIG. 2b is an electron microscope scanning image of the three-dimensional honeycomb carbon-based nanomaterial loaded with Zn element in example 3;
FIG. 3a is an electron microscope scanning image of the macroporous three-dimensional honeycomb carbon-based nanomaterial prepared under the condition of high molecular weight (50000-60000) polyvinyl alcohol in example 5;
FIG. 3b is an electron microscope scanning image of the three-dimensional honeycomb carbon-based nanomaterial loaded with Zn element in example 5.
Detailed Description
The present invention is further described in conjunction with electron microscope scans and examples to provide a better understanding of the nature of the invention. The reagent materials in the invention are all commercial products.
In the following examples, graphene oxide was obtained from Bailingwei technologies, Inc. and had a lamella diameter of 30 to 50 μm and a lamella thickness of 0.8 to 1.2 nm.
Example 1
In this embodiment, the specific steps for preparing the three-dimensional honeycomb carbon-based nanomaterial with adjustable zinc oxide loading aperture are as follows:
(1) preparing 5mL of 4mg/mL graphene oxide suspension water solution, and performing ultrasonic treatment for 30 min at the ambient temperature of 25 ℃, the ultrasonic frequency of 40KHz and the ultrasonic power of 250W to form uniform graphene suspension water solution.
(2) According to the following steps of 1:8, adding 2.5mg of zinc oxide into the graphene suspension water liquid obtained in the step (1), and performing ultrasonic treatment for 1 hour under the same ultrasonic condition as that in the step (1) to uniformly disperse the zinc oxide on graphene sheets to form a uniform zinc oxide-graphene dispersion liquid.
(3) According to the mass fraction of 10wt%, 0.5g of polyvinyl alcohol with low molecular weight (5000-10000) is added into 5mL of deionized water, heated to 100 ℃ and stirred to obtain a polyvinyl alcohol aqueous solution. And (3) mixing the obtained polyvinyl alcohol aqueous solution with the zinc oxide-graphene dispersion liquid obtained in the step (2), and performing ultrasonic treatment for 1 hour under the same ultrasonic condition as that in the step (1) to form uniform polyvinyl alcohol-zinc oxide-graphene oxide hydrogel.
(4) And (3) placing the polyvinyl alcohol-zinc oxide-graphene oxide hydrogel obtained in the step (3) into a cylindrical freezing pipe by using an ice template assembly method, freezing for 12 hours at the temperature of-70 ℃, placing the hydrogel into a vacuum freeze dryer with the vacuum degree of less than 20KPa and the temperature of-25 ℃ when the internal temperature of the hydrogel is consistent with the freezing temperature and does not change any more and liquid water in the hydrogel is completely changed into ice, and drying for 48 hours to obtain the cylindrical three-dimensional honeycomb carbon-based nanomaterial.
The sample micro-morphology was characterized using SEM, and the SEM image of the three-dimensional honeycomb carbon-based nanomaterial obtained in example 1 is shown in fig. 1 a. It can be seen that the microporous three-dimensional honeycomb carbon-based nanomaterial synthesized under the condition of using low molecular weight (5000-10000) polyvinyl alcohol has the pore diameter range of 40-60 um. The cross-linking agent polyvinyl alcohol with a linear structure in the pore diameter of the graphene enables the three-dimensional honeycomb carbon-based nano material to have good mechanical properties.
The mechanical properties of the obtained three-dimensional honeycomb carbon-based nano material are basically kept unchanged after 10 times of repeated compression cycles under the condition that the stress is 0.5 MPa. An SEM image of the three-dimensional honeycomb-shaped carbon-based nano material loaded with Zn element in example 1 is shown in FIG. 1b, and a large amount of zinc oxide is loaded on graphene sheets.
Example 2
In this embodiment, the specific steps for preparing the three-dimensional honeycomb carbon-based nanomaterial with adjustable zinc oxide loading aperture are as follows:
(1) preparing 5mL of graphene oxide suspension water liquid with the concentration of 4mg/mL, and carrying out ultrasonic treatment for 30 min at the ambient temperature of 25 ℃, the ultrasonic frequency of 40KHz and the ultrasonic power of 250W to form uniform graphene suspension water liquid.
(2) According to the following steps of 1: and 4, adding 5mg of zinc oxide into the graphene suspension water liquid obtained in the step (1) according to the mass ratio of the zinc oxide to the graphene, and performing ultrasonic treatment for 1 hour under the same ultrasonic condition as that in the step (1) to uniformly disperse the zinc oxide on graphene sheets to form a uniform zinc oxide-graphene dispersion liquid.
(3) According to the mass fraction of 10wt%, 0.5g of low molecular weight (5000-10000) polyvinyl alcohol is added into 5mL of deionized water, heated to 100 ℃ and stirred to obtain a polyvinyl alcohol aqueous solution. And (3) mixing the obtained polyvinyl alcohol aqueous solution with the zinc oxide-graphene dispersion liquid obtained in the step (2), and performing ultrasonic treatment for 1 hour under the same ultrasonic condition as that in the step (1) to form uniform polyvinyl alcohol-zinc oxide-graphene oxide hydrogel.
(4) And (3) placing the polyvinyl alcohol-zinc oxide-graphene oxide hydrogel obtained in the step (3) into a cylindrical freezing pipe by using an ice template assembly method, freezing for 12 hours at the temperature of-70 ℃, placing the hydrogel into a vacuum freeze dryer with the vacuum degree of less than 20KPa and the temperature of-25 ℃ when the internal temperature of the hydrogel is consistent with the freezing temperature and does not change any more and liquid water in the hydrogel is completely changed into ice, and drying for 48 hours to obtain the cylindrical three-dimensional honeycomb carbon-based nanomaterial.
The microscopic morphology of the sample is represented by SEM, and the aperture of the microporous three-dimensional honeycomb carbon-based nano material synthesized in example 2 under the condition of using low molecular weight (5000-10000) polyvinyl alcohol is 40-60 um. The cross-linking agent polyvinyl alcohol with a linear structure in the pore diameter of the graphene enables the three-dimensional honeycomb carbon-based nano material to have good mechanical properties. The mechanical properties of the obtained three-dimensional honeycomb carbon-based nano material are basically kept unchanged after 10 times of repeated compression cycles under the condition that the stress is 0.5 MPa.
Example 3
In this embodiment, the specific steps for preparing the three-dimensional honeycomb carbon-based nanomaterial with adjustable zinc oxide loading aperture are as follows:
(1) preparing 5mL of graphene oxide suspension water liquid with the concentration of 4mg/mL, and carrying out ultrasonic treatment for 30 min at the ambient temperature of 25 ℃, the ultrasonic frequency of 40KHz and the ultrasonic power of 250W to form uniform graphene suspension water liquid.
(2) According to the following steps of 1:8, adding 2.5mg of zinc oxide into the graphene suspension water liquid obtained in the step (1), and performing ultrasonic treatment for 1 hour under the same ultrasonic condition as that in the step (1) to uniformly disperse the zinc oxide on graphene sheets to form a uniform zinc oxide-graphene dispersion liquid.
(3) According to the mass fraction of 10wt%, 0.5g of polyvinyl alcohol with medium molecular weight (20000-25000) is added into 5mL of deionized water, heated to 100 ℃ and stirred to obtain a polyvinyl alcohol aqueous solution. And (3) mixing the obtained polyvinyl alcohol aqueous solution with the zinc oxide-graphene dispersion liquid obtained in the step (2), and performing ultrasonic treatment for 1 hour under the same ultrasonic condition as that in the step (1) to form uniform polyvinyl alcohol-zinc oxide-graphene oxide hydrogel.
(4) And (3) placing the polyvinyl alcohol-zinc oxide-graphene oxide hydrogel obtained in the step (3) into a cylindrical freezing pipe by using an ice template assembly method, freezing for 12 hours at the temperature of-70 ℃, placing the hydrogel into a vacuum freeze dryer with the vacuum degree of less than 20KPa and the temperature of-25 ℃ when the internal temperature of the hydrogel is consistent with the freezing temperature and does not change any more and liquid water in the hydrogel is completely changed into ice, and drying for 48 hours to obtain the cylindrical three-dimensional honeycomb carbon-based nanomaterial.
The microscopic morphology of the sample is characterized by using SEM, an SEM image of the three-dimensional honeycomb carbon-based nano material obtained in example 3 is shown in figure 2a, and the pore diameter of the microporous three-dimensional honeycomb carbon-based nano material synthesized by using polyvinyl alcohol with the molecular weight of 20000-25000 is 100-120 um. The cross-linking agent polyvinyl alcohol with a linear structure in the pore diameter of the graphene enables the three-dimensional honeycomb carbon-based nano material to have good mechanical properties. The mechanical properties of the obtained three-dimensional honeycomb carbon-based nano material are basically kept unchanged after 10 times of repeated compression cycles under the condition that the stress is 0.5 MPa. An SEM image of the three-dimensional honeycomb-shaped carbon-based nano material loaded with Zn element in example 3 is shown in FIG. 2b, and a large amount of zinc oxide is loaded on graphene sheets.
Example 4
In this embodiment, the specific steps for preparing the three-dimensional honeycomb carbon-based nanomaterial with adjustable zinc oxide loading aperture are as follows:
(1) preparing 5mL of graphene oxide suspension water liquid with the concentration of 4mg/mL, and carrying out ultrasonic treatment for 30 min at the ambient temperature of 25 ℃, the ultrasonic frequency of 40KHz and the ultrasonic power of 250W to form uniform graphene suspension water liquid.
(2) According to the following steps of 1: and 4, adding 5mg of zinc oxide into the graphene suspension water liquid obtained in the step (1) according to the mass ratio of the zinc oxide to the graphene, and performing ultrasonic treatment for 1 hour under the same ultrasonic condition as that in the step (1) to uniformly disperse the zinc oxide on graphene sheets to form a uniform zinc oxide-graphene dispersion liquid.
(3) According to the mass fraction of 10wt%, 0.5g of polyvinyl alcohol with medium molecular weight (20000-25000) is added into 5mL of deionized water, heated to 100 ℃ and stirred to obtain a polyvinyl alcohol aqueous solution. And (3) mixing the obtained polyvinyl alcohol aqueous solution with the zinc oxide-graphene dispersion liquid obtained in the step (2), and performing ultrasonic treatment for 1 hour under the same ultrasonic condition as that in the step (1) to form uniform polyvinyl alcohol-zinc oxide-graphene oxide hydrogel.
(4) And (3) placing the polyvinyl alcohol-zinc oxide-graphene oxide hydrogel obtained in the step (3) into a cylindrical freezing pipe by using an ice template assembly method, freezing for 12 hours at the temperature of-70 ℃, placing the hydrogel into a vacuum freeze dryer with the vacuum degree of less than 20KPa and the temperature of-25 ℃ when the internal temperature of the hydrogel is consistent with the freezing temperature and does not change any more and the liquid water in the hydrogel is completely changed into ice, and drying for 48 hours to obtain the cylindrical three-dimensional honeycomb carbon-based nano material.
The microscopic morphology of the sample is characterized by using SEM, and in example 4, the aperture of the microporous three-dimensional honeycomb carbon-based nano material synthesized by using polyvinyl alcohol with the molecular weight of 10000-25000 is 100-120 um. The cross-linking agent polyvinyl alcohol with a linear structure in the pore diameter of the graphene enables the three-dimensional honeycomb carbon-based nano material to have good mechanical properties. The mechanical properties of the obtained three-dimensional honeycomb carbon-based nano material are basically kept unchanged after 10 times of repeated compression cycles under the condition that the stress is 0.5 MPa.
Example 5
In this embodiment, the specific steps for preparing the three-dimensional honeycomb carbon-based nanomaterial with adjustable zinc oxide loading aperture are as follows:
(1) preparing 5mL of graphene oxide suspension water liquid with the concentration of 4mg/mL, and carrying out ultrasonic treatment for 30 min at the ambient temperature of 25 ℃, the ultrasonic frequency of 40KHz and the ultrasonic power of 250W to form uniform graphene suspension water liquid.
(2) According to the following steps of 1:8, adding 2.5mg of zinc oxide into the graphene suspension water liquid obtained in the step (1), and performing ultrasonic treatment for 1h under the same ultrasonic condition as that in the step (1) to uniformly disperse the zinc oxide on graphene sheets to obtain the zinc oxide-graphene dispersion liquid.
(3) According to the mass fraction of 10wt%, 0.5g of high molecular weight (50000-60000) polyvinyl alcohol is added into 5mL of deionized water, heated to 100 ℃ and stirred to obtain a polyvinyl alcohol aqueous solution. And (3) mixing the obtained polyvinyl alcohol aqueous solution with the aqueous solution in the step (2), and carrying out ultrasonic treatment for 1h under the same ultrasonic condition as that in the step (1) to form uniform polyvinyl alcohol-zinc oxide-graphene oxide hydrogel.
(4) And (3) placing the polyvinyl alcohol-zinc oxide-graphene oxide hydrogel obtained in the step (3) into a cylindrical freezing pipe by using an ice template assembly method, freezing for 12 hours at the temperature of-70 ℃, placing the hydrogel into a vacuum freeze dryer with the vacuum degree of less than 20KPa and the temperature of-25 ℃ when the internal temperature of the hydrogel is consistent with the freezing temperature and does not change any more and the liquid water in the hydrogel is completely changed into ice, and drying for 48 hours to obtain the cylindrical three-dimensional honeycomb carbon-based nano material.
An SEM is used for representing the microscopic morphology of a sample, an SEM image of the three-dimensional honeycomb carbon-based nano material obtained in example 5 is shown in figure 3a, and the aperture of the microporous three-dimensional honeycomb carbon-based nano material synthesized under the condition of using high molecular weight (50000-60000) polyvinyl alcohol is 280-300 um. The cross-linking agent polyvinyl alcohol with a linear structure in the pore diameter of the graphene enables the three-dimensional honeycomb carbon-based nano material to have good mechanical properties. The mechanical properties of the obtained three-dimensional honeycomb carbon-based nano material are basically kept unchanged after 10 times of repeated compression cycles under the condition that the stress is 0.5 MPa. An SEM image of the three-dimensional honeycomb-shaped carbon-based nano material loaded with Zn element in example 5 is shown in FIG. 3b, and a large amount of zinc oxide is loaded on graphene sheets.
Example 6
In this embodiment, the specific steps for preparing the three-dimensional honeycomb carbon-based nanomaterial with adjustable zinc oxide loading aperture are as follows:
(1) preparing 5mL of graphene oxide suspension water liquid with the concentration of 4mg/mL, and carrying out ultrasonic treatment for 30 min at the ambient temperature of 25 ℃, the ultrasonic frequency of 40KHz and the ultrasonic power of 250W to form uniform graphene suspension water liquid.
(2) According to the following steps of 1: 4, adding 5mg of zinc oxide into the graphene suspension water liquid obtained in the step (1), and performing ultrasonic treatment for 1h under the same ultrasonic condition as that in the step (1) to uniformly disperse the zinc oxide on graphene sheets to obtain the zinc oxide-graphene dispersion liquid.
(3) According to the mass fraction of 10wt%, 0.5g of polyvinyl alcohol with high molecular weight (50000-60000) is added into 5mL of deionized water, heated to 100 ℃ and stirred to obtain a polyvinyl alcohol aqueous solution. And (3) mixing the obtained polyvinyl alcohol aqueous solution with the aqueous solution in the step (2), and carrying out ultrasonic treatment for 1h under the same ultrasonic condition as that in the step (1) to form uniform polyvinyl alcohol-zinc oxide-graphene oxide hydrogel.
(4) And (3) placing the polyvinyl alcohol-zinc oxide-graphene oxide hydrogel obtained in the step (3) into a cylindrical freezing pipe by using an ice template assembly method, freezing for 12 hours at the temperature of-70 ℃, placing the hydrogel into a vacuum freeze dryer with the vacuum degree of less than 20KPa and the temperature of-25 ℃ when the internal temperature of the hydrogel is consistent with the freezing temperature and does not change any more and the liquid water in the hydrogel is completely changed into ice, and drying for 48 hours to obtain the cylindrical three-dimensional honeycomb carbon-based nano material.
The microscopic morphology of the sample is represented by SEM, and in example 6, the macroporous three-dimensional honeycomb carbon-based nano material synthesized by using high molecular weight (50000-60000) polyvinyl alcohol has the pore diameter ranging from 280-300 um. The cross-linking agent polyvinyl alcohol with a linear structure in the aperture of the graphene enables the three-dimensional honeycomb carbon-based nano material to have good mechanical properties, and the mechanical properties of the obtained three-dimensional honeycomb carbon-based nano material are basically kept unchanged after 10 times of repeated compression cycles under the condition that the stress is 0.5 MPa.
As can be seen from the electron microscope scanning images of the three-dimensional honeycomb carbon-based nano materials obtained in examples 1, 3 and 5, the pore size of the three-dimensional honeycomb carbon-based nano material increases with the increase of the molecular weight of the polyvinyl alcohol. The pore size of the three-dimensional honeycomb carbon-based nano material can be accurately regulated and controlled by the polyvinyl alcohol. The three-dimensional honeycomb carbon-based nano material synthesized under the condition of adding the high molecular weight polyvinyl alcohol has an oversized pore diameter structure and extremely strong adsorption performance. Meanwhile, due to the existence of polyvinyl alcohol, a large amount of zinc can be loaded on the graphene sheet, and the photocatalytic performance of the graphene sheet is greatly enhanced.
Application example 1:
and (3) carrying out a photocatalytic test on nitrobenzene under the irradiation condition of an ultraviolet lamp by using the three-dimensional honeycomb carbon-based nano material obtained in the embodiment 1-6.
The test conditions were: 100 mL of nitrobenzene water solution with the concentration of 10 mg/L is measured and put into a photoreactor, 4mg of three-dimensional honeycomb carbon-based nano material is added, and the mixture is magnetically stirred for 30 min in a dark place to achieve adsorption-desorption balance. Opening a medium-pressure mercury lamp with an emission spectrum between 200nm and 600nm for photocatalytic reaction, and performing sampling detection at regular time for 2 h. Nitrobenzene concentration was measured by High Performance Liquid Chromatography (HPLC), UV detector, 4X 150 mm SB-C18 column (Agilent). 50% methanol: 50% distilled water (v: v) at a wavelength of 268 nm and a flow rate of 1.0 mL/min. The results are shown in Table 1.
The experimental results of comparative examples 1-2, examples 3-4 and examples 5-6 show that under the condition of the same pore diameter, the photocatalytic conversion rate of the three-dimensional honeycomb carbon-based nano material p-nitrobenzene can be improved by properly increasing the Zn loading amount. The experimental results of comparative examples 1, 3 and 5 and examples 2, 4 and 6 show that the three-dimensional honeycomb carbon-based nano material with the mesoporous structure is more beneficial to the photocatalytic conversion of p-nitrobenzene under the condition of the same Zn ion loading. The reason is that the specific surface area of the three-dimensional honeycomb carbon-based nano material with the small pore structure is small, the Zn ion loading sites are few, so that the Zn ions are mutually agglomerated, although the three-dimensional honeycomb carbon-based nano material with the large pore structure has a great specific surface area, graphene sheets in the three-dimensional honeycomb carbon-based nano material are easy to curl, so that the loaded Zn ions are unevenly distributed on graphene sheet layers, and the factors influence the photocatalytic conversion rate of nitrobenzene. The three-dimensional honeycomb carbon-based nano material with the mesoporous structure has a relatively large specific surface area and a more regular pore channel structure, and can realize large and uniform load of Zn ions. The three-dimensional honeycomb carbon-based nano material can efficiently catalyze and convert nitrobenzene under a mesoporous structure.
Figure DEST_PATH_IMAGE001
The above-described embodiment is only a preferred embodiment of the present invention. For example, in the above embodiments, the crosslinking agent polyvinyl alcohol used for regulating the pore size of the three-dimensional honeycomb carbon-based nanomaterial may be replaced by other types of crosslinking agents, so long as the crosslinking agents can connect graphene sheets to support the porous structure of the aerogel and realize a large amount of loading of zinc oxide on the graphene sheets, and the effects of the present invention can also be realized. As another example, zinc oxide, which is a semiconductor material, is used as a photocatalyst in the above-described embodiment, and may be replaced with another semiconductor material, such as TiO2、SnO2、ZrO2And the technical effects of the present invention can be achieved.
Thus, variations can be made by those skilled in the art without departing from the basic principles of the method of the present invention. However, the invention is intended to cover the protection scope of the present invention by adopting the equivalent or equivalent method.

Claims (7)

1. A preparation method of a three-dimensional honeycomb carbon-based nano material with adjustable zinc oxide load aperture is characterized by comprising the following steps:
1) adding graphene oxide into water, and uniformly dispersing by using ultrasonic waves to obtain a graphene oxide suspension;
2) adding zinc oxide into the graphene oxide suspension obtained in the step 1), and uniformly mixing by ultrasonic to obtain a zinc oxide-graphene oxide dispersion liquid;
3) adding polyvinyl alcohol into deionized water, heating, stirring and dissolving to obtain a polyvinyl alcohol aqueous solution; mixing the polyvinyl alcohol aqueous solution with the zinc oxide-graphene oxide dispersion liquid obtained in the step 2), and performing ultrasonic treatment for 0.5-2 h to obtain polyvinyl alcohol-zinc oxide-graphene oxide hydrogel;
4) and (3) putting the polyvinyl alcohol-zinc oxide-graphene oxide hydrogel obtained in the step (3) into a cylindrical freezing pipe by adopting an ice template assembly method, freezing at a low temperature, and putting the hydrogel into a vacuum freeze dryer for drying treatment when the internal temperature of the polyvinyl alcohol-zinc oxide-graphene oxide hydrogel is consistent with the freezing temperature and does not change any more and the liquid water in the hydrogel is completely changed into ice, so as to obtain the cylindrical three-dimensional honeycomb carbon-based nano material with the porous structure.
2. The preparation method of the zinc oxide-loaded pore size-adjustable three-dimensional honeycomb carbon-based nanomaterial according to claim 1, wherein in step 1), the sheet size of the graphene oxide is greater than 30 um, and the concentration of the prepared graphene oxide suspension is 2-6 mg/L, preferably 3-4 mg/L.
3. The preparation method of the three-dimensional honeycomb carbon-based nanomaterial with the adjustable zinc oxide loading pore diameter according to claim 1, wherein in the step 2), the particle size of the zinc oxide is 10-30 nm, and the mass ratio of the zinc oxide to the graphene oxide in the graphene oxide suspension is 1: 5-1: 10, preferably 1: 7-1: 8.
4. The preparation method of the zinc oxide-loaded three-dimensional honeycomb carbon-based nanomaterial with the adjustable pore diameter according to claim 1, wherein in the polyvinyl alcohol aqueous solution obtained in the step 3), the mass ratio of polyvinyl alcohol to deionized water is 6-12: 100, preferably 9-10: 100; and 3) mixing the polyvinyl alcohol aqueous solution with the zinc oxide-graphene oxide dispersion liquid, wherein the mass ratio of the polyvinyl alcohol to the graphene oxide is 20-30: 1.
5. The preparation method of the zinc oxide-loaded pore-diameter-adjustable three-dimensional honeycomb carbon-based nanomaterial according to claim 1, wherein in the step 1), the step 2) or the step 3), the environmental temperature in the ultrasonic process is room temperature, the ultrasonic frequency is 30-50 KHz, and the ultrasonic power is 200-300W.
6. The preparation method of the three-dimensional honeycomb carbon-based nanomaterial with the adjustable zinc oxide supported pore diameter according to claim 1, wherein the molecular weight of the polyvinyl alcohol is 5000-60000, preferably 20000-25000.
7. The preparation method of the three-dimensional honeycomb carbon-based nanomaterial with the adjustable zinc oxide loading aperture according to claim 1, wherein in the step 4), the low-temperature freezing time is 10-15 hours, and the low-temperature freezing temperature is-80 ℃ to-70 ℃; the drying time is 40-50 h, and the drying temperature is-30 ℃ to-20 ℃.
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