CN113003568A

CN113003568A - Defect-state monolayer graphene film and preparation method and application thereof

Info

Publication number: CN113003568A
Application number: CN202110392417.7A
Authority: CN
Inventors: 宋也男; 吴文杰; 孙卓
Original assignee: East China Normal University
Current assignee: East China Normal University
Priority date: 2021-04-13
Filing date: 2021-04-13
Publication date: 2021-06-22
Anticipated expiration: 2041-04-13
Also published as: CN113003568B

Abstract

The invention discloses a defect-state single-layer graphene film, a preparation method and application thereof, wherein the preparation method comprises the following steps: placing the copper foil in a low pressure CVD system at H₂Under the protection of an/Ar reducing atmosphere, carrying out high-temperature catalytic cracking on methane molecules to grow a single-layer graphene film on the surface of the copper foil; then transferring the graphene film on the copper foil to SiO by using a wet transfer process₂a/Si substrate; and constructing a new defect site on the surface of the graphene film by using a plasma etching technology. The defect-state single-layer graphene prepared by the invention is used as a catalyst, ozone molecules are adsorbed near edge active sites under the action of ozone, and OH is generated through the transfer catalysis of intermolecular charges, so that the organic pollutants in the water environment are efficiently removed.

Description

Defect-state monolayer graphene film and preparation method and application thereof

Technical Field

The invention belongs to the technical field of water treatment, and particularly relates to a preparation method for preparing a defect-state single-layer graphene film and application of the defect-state single-layer graphene film in ozone catalytic degradation.

Background

Ozone catalytic oxidation is a novel oxidation technology developed in recent years and applied to environmental improvement and restoration. Ozone generatorThe molecules, due to their high oxidation potential (2.07V), can oxidize most organic contaminants directly in water or on the surface of catalysts. The pure ozone oxidation technology has the problem of poor product selectivity, and byproducts are often harmful small molecular organic matters and still have threat to the environment. Use of a catalyst to induce reactive oxygen free radicals (& OH, & O) from the cleavage of ozone molecules₂ ^-And¹O₂etc.) can enrich the oxidation mode of the polluted substrate, not only can improve the utilization efficiency of ozone molecules, but also the active oxygen free radicals with higher oxidation capacity can improve the mineralization efficiency of the polluted substrate and can be directly converted into pollution-free CO₂And H₂O。

Currently, the most commonly used ozone catalysts are primarily metal oxides (MnO)₂、Ni₂O₃、Co₂O₃、Fe₂O₃、CuO、Al₂O₃、TiO₂Etc.), minerals (ZnFe)₂O₄、NiFe₂O₄、Ce_0.1Fe_0.9OOH, etc.) and nanocarbon catalysts (activated carbon, graphene, carbon nanotubes, etc.). Compared with a metal-based catalyst containing metal elements, the nano-carbon catalyst can not only reduce the operation cost of the ozone catalysis technology, but also completely avoid the problem that secondary environmental pollution is easily caused by metal ions dissolved out. Oxygen-containing functional groups, structural defect sites, heteroatom doping sites, and electron-rich sites on the surface of the nanocarbon material are generally attributed to ozone-activated reaction centers. Through the development of the last two decades, the carbon-based catalyst has made great progress in efficiency improvement and catalytic mechanism disclosure. However, due to the previously reported carbon-based catalysts, a macroscopic bulk, powder or multi-layered nanocarbon catalyst was used. The graphene catalyst has low atom utilization efficiency, and the powdered carbon catalyst is difficult to recover and separate in the actual water environment remediation, which is not beneficial to the actual industrial application and popularization.

Therefore, the carbon-based catalyst which has high atom utilization rate and high catalytic efficiency and is easy to recycle and separate is provided to be applied to the ozone catalyst technology, and the application is very urgent.

Disclosure of Invention

The problems to be solved by the invention are: the existing graphene-based catalyst has the problems of low atom utilization efficiency and difficult catalyst recovery and separation in the application of ozone catalysis technology.

In order to solve the problems, the invention provides a defect-state single-layer graphene film, a preparation method and application thereof.

The specific technical scheme for realizing the purpose of the invention is as follows:

a preparation method of a defect-state single-layer graphene film comprises the following steps:

step 1): placing the copper foil in the middle of a quartz tube of a CVD system, and introducing reducing gas H at a flow rate of 100-300sccm₂A mixed gas of/Ar; wherein H₂The proportion of the/Ar mixed gas is 10-90%, and the pressure of a CVD system is controlled to be 5-10 Pa;

step 2): the CVD tube furnace was ramped up from 25 ℃ to 900 ℃ in 1.5 hours, followed by ramping up from 900 ℃ to 1000 ℃ in 30 minutes; introducing methane gas at a flow rate of 15-100sccm, and controlling the decomposition and growth time of methane to be 1-2 hours; obtaining a single-layer graphene film growing on the copper foil;

step 3): placing the copper foil with the single-layer graphene film grown thereon obtained in the step 2) on a KW-5 type desk-top spin coater, and coating a layer of PMMA solution on the surface; the rotating speed of the table type spin coater is 50 kilorevolutions per minute, and the spin time is 15-30 seconds;

step 4): immersing the copper foil coated with PMMA on the surface obtained in the step 3) into FeCl with the concentration of 1-5mol/L₃Etching the copper foil in the solution for 4-10 hours, and floating a layer of PMMA graphene film on the surface of the solution;

step 6): SiO for the graphene film of the PMMA floating in the step 5)₂Fishing out the Si piece, and washing the Si piece for 3 to 5 times by using deionized water;

step 7): SiO of the PMMA-loaded graphene film obtained in the step 6)₂Putting the Si sheet in an oven, and drying at 60-100 ℃ for 0.5-2 hours;

step 8): the SiO dried in the step 7) is added₂Soaking the Si sheet in an acetone solution to etch PMMA;

step 9): SiO etched in the step 8)₂Transferring the/Si sheet into a plasma cleaning machine, and etching the graphene film; the power of the plasma cleaning machine is 700-900w, and the etching time is 2-6 seconds; and obtaining the defect-state single-layer graphene film.

The defect-state single-layer graphene film prepared by the method.

The application of the defect-state single-layer graphene film in catalytic degradation of sulfamethoxazole by ozone comprises the following specific steps: SiO loaded with defect-state monolayer graphene film₂After the/Si substrate is fixed in the water solution rich in the sulfamethoxazole, ozone gas generated by an ozone generator is introduced into the water solution, ozone molecules generate a large amount of OH on the surface of the graphene film, the sulfamethoxazole in the water solution is oxidized and degraded, and after the ozone is introduced into the water solution for 60 minutes, the degradation efficiency of the sulfamethoxazole in the water solution reaches 94.65%. And (3) degrading and removing organic pollutants under the action of ozone gas by taking the defect-state single-layer graphene film as a catalyst.

Compared with the prior art, the invention has the following beneficial effects:

(1) the preparation raw materials of the defect-state single-layer graphene film are simple and easy to obtain, the preparation period is short, and the raw materials and the preparation cost are low;

(2) the prepared defect-state single-layer graphene film has higher atom utilization efficiency, and ozone catalytic decomposition mainly occurs on the surface of the catalyst, so that the use cost of the graphene catalyst can be reduced in the catalytic reaction of the single-layer graphene film;

(3) the prepared single-layer defect state graphene film has more edge defects and can provide more catalytic sites;

(4) the defect-state single-layer graphene film has the advantages of excellent stability and persistence, easiness in separation and recovery in practical industrial application and the like.

Drawings

FIG. 1 is a scanning electron microscope image of a defective monolayer graphene film prepared in example 1 of the present invention;

FIG. 2 is a view showing the construction of an apparatus for catalyzing ozone in example 2 of the present invention;

FIG. 3 is a graph comparing the degradation efficiency of sulfamethoxazole with a defective monolayer graphene film according to example 2 of the present invention and an original monolayer graphene film according to comparative example 1;

FIG. 4 is a graph comparing the catalytic stability of ozone in a defect state single-layer graphene thin film in example 2 of the present invention.

Detailed Description

In order to make the invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.

Example 1

(1) placing copper foil 9cm × 9cm in a low pressure CVD furnace, controlling the pressure of the CVD tube furnace at 5Pa, and introducing 10% H₂The flow rate of the gas is 100sscm, and the temperature rising program of the tube furnace is as follows: the temperature of the tube furnace was raised from 25 ℃ to 900 ℃ within 1.5 hours, then to 1000 ℃ within 0.3 hours, and 99.99% methane gas was introduced for 1 hour. Then CVD furnace in H₂Cooling to room temperature under the atmosphere of/Ar to obtain a single-layer graphene film growing on the copper foil;

(2) spin-coating a layer of 8 wt% PMMA solution on the surface of the copper foil with graphene growing on the surface obtained in the step (1), drying at 60 ℃ for 1 hour, and immersing into 1mol/L FeCl₃The solution was soaked for 4 hours. After the copper foil is etched, SiO of 9cm multiplied by 9cm is used₂The graphene film is fished out from the/Si sheet, and is washed 3 times by deionized water in the process. Placing the treated graphene film in an oven, and drying for 1 hour at the temperature of 60 ℃; immersing the graphene film on the dried SiO2/Si sheet into an acetone solution, and etching for 24 hours;

(3) transferring the product obtained in (2) toSiO₂Cutting the graphene film on the/Si sheet into a size of 3cm multiplied by 3 cm. The substrate was placed in a plasma cleaner and etched for a period of 6 seconds at a power of 700 w. A defective graphene thin film was obtained (transmission electron microscopy image is shown in fig. 1). After plasma etching, except the domain boundary of the original graphene, the surface of the graphene film is provided with a plurality of micropores with the pore diameter of 1-2 microns, and has more edge sites.

Example 2

The application of the defect-state single-layer graphene film in ozone catalytic degradation of sulfamethoxazole is as follows:

as shown in FIG. 2, three sheets of the defect-state single-layer graphene thin film prepared in example 1 were placed in 50ml of 1mg/L aqueous solution of Neonomine, and ozone gas was introduced into the aqueous solution at a flow rate of 100sscm in the direction of the arrow in the figure in FIG. 2, wherein: teflon hose 1, iron stand clamp 2, transfer to SiO₂Graphene catalyst 3 on the Si piece, polytetrafluoroethylene fixed slot 4, experiment platform 5, iron stand platform branch 6, beaker 7. After the ozone gas acts for 10 minutes, 2ml of reaction solution is taken, the concentration of the sulfamethoxazole in the water solution after the reaction is detected by using high performance liquid chromatography, and the catalytic reaction is finished after the reaction system is carried out for 60 min.

Comparative example 1

This comparative example differs from example 2 in that the catalyst used an unetched graphene film.

Comparative example 2

The comparative example differs from example 2 in that the catalyst used in example 2 was a single-layer graphene thin film catalyst.

Comparative example 3

The comparative example is different from example 2 in that the catalyst is the single-layer graphene thin film catalyst used in comparative example 2;

comparative example 4

The present comparative example is different from example 2 in that the catalyst used in comparative example 3 is a single-layer graphene thin film catalyst.

The experimental data of example 2 and comparative example 1 are shown in fig. 3, and the degradation efficiency of the original single-layer graphene film is 40.17% under the same ozone action, while the degradation efficiency is improved to 94.65% after the plasma etching. In the invention, the defect-state graphene film after plasma etching has more edge sites, and the created electron-rich region can excite and decompose ozone molecules by the transfer of intermolecular charges to generate highly-oxidative OH, thereby completing the oxidative degradation of the sulfamethoxazole. As can be seen from the data in fig. 4, the used defect-state graphene film has good cycling stability, and the degradation of the sulfamethoxazole can still reach more than 80% after four times of cycling.

Claims

1. A preparation method of a defect-state single-layer graphene film is characterized by comprising the following steps:

step 7): carrying out the step 6) to obtain the PMMA-loaded grapheneSiO of thin film₂Putting the Si sheet in an oven, and drying at 60-100 ℃ for 0.5-2 hours;

step 9): SiO etched in the step 8)₂and/Si sheets are transferred into a plasma cleaning machine, the graphene film is etched, the power of the plasma cleaning machine is set to be 700-900w, and the etching time is 2-6 seconds, so that the defect-state single-layer graphene film is obtained.

2. A defective monolayer graphene film produced by the method of claim 1.

3. The application of the defect-state single-layer graphene film of claim 2 in ozone catalytic degradation of sulfamethoxazole.

4. The application of claim 3, wherein the specific process comprises: SiO loaded with defect-state monolayer graphene film₂After the/Si sheet is fixed in the water solution rich in the sulfamethoxazole, ozone gas generated by an ozone generator is introduced into the water solution, ozone molecules generate a large amount of OH on the surface of the graphene film, the sulfamethoxazole in the water solution is oxidized and degraded, and after the ozone is introduced into the water solution for 60 minutes, the degradation efficiency of the sulfamethoxazole in the water solution reaches 94.65%.