KR102480996B1 - Preparation method of porous composite membrane having graphene layer formed by laser photothermal pyrolysis and application thereof - Google Patents

Abstract

The present invention relates to a method for manufacturing a porous polymer composite film having a three-dimensional graphene layer formed thereon using a laser carbonization technique and to an application of the porous composite film prepared therefrom, and more specifically, preparing a porous polymer film; and irradiating a laser on one surface of the porous polymer film to carbonize a region having a predetermined thickness in the thickness direction of the polymer film to form a graphene layer. A method of manufacturing a porous composite film having a laser carbonized graphene layer, It relates to a solar-based steam generation system using the photothermal properties of the porous composite membrane prepared therefrom.

Description

Preparation method of porous composite membrane having graphene layer formed by laser photothermal pyrolysis and application thereof}

The present invention relates to a method for manufacturing a porous polymer composite membrane having a three-dimensional graphene layer formed thereon using a laser carbonization technique and an application of the porous composite membrane prepared therefrom.

More specifically, preparing a porous polymer film; and irradiating a laser on one surface of the porous polymer film to carbonize a region having a predetermined thickness in the thickness direction of the polymer film to form a graphene layer. A method of manufacturing a porous composite film having a laser carbonized graphene layer, It relates to a solar-based steam generation system using the photothermal properties of the porous composite membrane prepared therefrom.

Solar water evaporation technology, which is a combination of solar energy harvesting technology and water purification technology, is receiving a lot of attention in order to solve the problem of increasing water and energy shortages through an eco-friendly method. Solar-powered steam generation floats a functional film on top of water, and the film receives sunlight and converts it into heat, while at the same time inducing the water below to be raised by capillary action. At this time, the lifted water is converted into steam by the generated heat, and the generated steam is collected and used as purified water. As a functional membrane that effectively converts sunlight into heat and generates steam, the development of membrane technology with a multi-layer structure made of materials having different properties is a major development direction in the above field. The upper layer receiving sunlight is composed of a photothermal material with a porous structure that can efficiently convert light into heat, and the lower layer is composed of a porous material that insulates the generated heat and draws up water by capillarity. it is ideal

In order to fabricate a multilayer structure film having these characteristics, it is common to configure a graphene-based porous material having excellent photothermal properties as an upper layer and a porous polymer material having insulating properties and hydrophilic properties as a lower layer. However, it has the disadvantage of requiring a lot of thermal/chemical energy and generating pollutants to produce graphene, as well as electrospinning to form the manufactured graphene-based material into a porous polymer and a multilayer structure. Alternatively, it is also a disadvantage that an additional process such as filtration is required. Meanwhile, in order to produce efficient graphene-based materials, Professor James M Tour's research team at Rice University in Texas, USA, simply irradiates a polymer containing a lot of aromatic hydrocarbons such as commercial polyimide (PI) with a laser. It has been reported that some polymers on the surface can be converted into porous graphene having a three-dimensional structure when irradiated, forming a bilayer structure composed of porous graphene and the remaining polymer substrate. However, even if this method is used, an open pore structure exists in the carbon of the porous graphene layer, but the lower polymer substrate is still a non-porous closed structure, so that the structure composed of such a double layer is practically difficult to apply to various fields.

US Patent Publication No. US2019/0088420. US Patent Publication No. US2017/0062821.

H. Ghasemi, G. Ni, A. M. Marconnet, J. Loomis, S. Yerci, N. Miljkovic and G. Chen, Nat. Commun., 2014, 5, 4449.

The present invention was developed to solve the above problems, and through a laser carbonization technique, a layer having excellent photo-thermal properties of hydrophobicity is formed on the upper side, but a porous composite membrane capable of maintaining a porous foam layer having hydrophilic property on the lower side is manufactured. It aims to provide a method for

In addition, the present invention is to provide a solar-based water purification method using a porous composite membrane having a laser carbonized graphene layer.

In the present invention, preparing a porous polymer film to solve the above problems; and forming a graphene layer by irradiating a laser beam on one surface of the porous polymer film to carbonize an area having a predetermined thickness in the thickness direction of the polymer film. to provide.

In addition, in the present invention, the graphene layer is formed in a region having a predetermined thickness in the thickness direction of the polyimide foam, and the light absorbance is 97% or more in the light wavelength range of 250 to 2500 nm, or the water contact angle of the graphene layer is 130 ° or more, and the water contact angle of the polyimide foam itself is 80 ° or less.

According to the present invention, there is an advantage that can be applied as a functional membrane by combining the advantages of a porous polymer and the advantages of a graphene-based material.

In particular, when irradiating a polyimide foam having a porous structure with a laser, graphene, a three-dimensional porous carbon, is formed on the upper part of the porous polymer foam, and the pore characteristics of the porous polymer foam can be maintained at the lower part. There is an effect.

The manufacturing method according to the present invention requires less thermal/chemical energy compared to conventional manufacturing methods of similar materials, and has economic feasibility because it can be manufactured in a relatively short time.

In addition, the porous composite membrane having a laser carbonized graphene layer according to the present invention can be usefully used as a functional solar thermal water purification membrane because a hydrophilic polymer material and graphene having excellent heat dissipation and photothermal characteristics are fused together.

1 schematically illustrates a manufacturing process of a porous composite membrane having a laser carbonized graphene layer according to an embodiment of the present invention.
Figure 2 shows the results of Raman analysis of the laser carbonized graphene layer according to one embodiment of the present invention.
Figure 3 shows the results of UV-Vis absorption spectroscopy of the laser carbonized graphene layer according to an embodiment of the present invention.
4 shows an electron microscope analysis and water contact angle of a laser carbonized graphene layer and a porous polymer according to an embodiment of the present invention.
5 shows the results of isotherm analysis of Ar to determine the pore characteristics and specific surface area of the laser carbonized graphene layer according to an embodiment of the present invention.
6 is an infrared image analysis result for confirming a phenomenon in which the porous composite film having a laser carbonized graphene layer according to an embodiment of the present invention converts sunlight into heat.
FIG. 7 shows the result of quantifying the amount of water vapor generated when the porous composite membrane having a laser carbonized graphene layer according to an embodiment of the present invention converts sunlight into heat.
Figure 8 shows the amount of ions when the porous composite membrane having a laser carbonized graphene layer according to an embodiment of the present invention converts sunlight into heat to purify seawater.

Hereinafter, the present invention will be described in detail. The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

In the present invention, preparing a porous polymer film to solve the above problems; and forming a graphene layer by irradiating a laser beam on one surface of the porous polymer film to carbonize an area having a predetermined thickness in the thickness direction of the polymer film. to provide.

In the manufacturing method according to one embodiment of the present invention, the porous polymer film may be a porous polyimide foam, and in this case, the polyimide foam preferably has a chemical structure represented by Formula 1 below. .

<Formula 1>

In Formula 1, n is an integer of 1 to 2,500 as a repeating unit.

In particular, in the production of polyamic acid, polyamic acid can be polymerized by reacting various dianhydride and diamine monomers in a polar aprotic solvent such as NMP, DMF, or DMAc. At this time, the polymerized polyamic acid is precipitated in acetone, grinded with a mixer to effectively remove the organic solvent inside, the precipitate is obtained through a filter, and the process of washing with acetone is repeated three times to obtain a purified polyamic acid precipitate, and at 40 ° C. Polyamic acid particles may be prepared by vacuum drying for 12 hours or more.

In the manufacturing method according to one embodiment of the present invention, the porous polyimide foam is oil using polyamic acid (PAA) of an aqueous phase and an organic solvent of an oil phase. Preparing high internal phase emulsions (HIPEs) of in-water (O/w); freeze-drying the high internal phase emulsions (HIPEs); and thermal imidization or chemical imidization of the freeze-dried high internal phase emulsion.

Next, polyamic acid particles are put in distilled water together with a water-solubilizer (amines, imidazoles) equivalent to twice the amount of the prepared polyamic acid and sufficiently stirred (1 hour to 48 hours) to prepare an aqueous solution of polyamic acid. At this time, the stirring time is different depending on 1) the polyamic acid solid content, 2) the type of water-soluble agent, and 3) the molecular structure of the polyamic acid, but most of them can be water-soluble within 48 hours.

In general, it is very difficult to prepare polyamic acid in the form of an aqueous solution, but in the present invention, an aqueous solution of polyamic acid is prepared to prepare a polyimide foam, and at this time, it is preferable to use an amine-based or imidazole-based water-solubilizing agent , Representative water-soluble agents such as 2-Dimethylaminoethanol (DMEA) and Triethylamine (TEA) can be used.

Additionally, the amine-based water-soluble agent includes, but is not limited to, 2-Dimethylaminoethanol (DMEA), N, N-Diethylethanolamine (DEEA), 3-Dimethylaminopropanol, Diethanolamine (DEA), 3-Diethylamino-1-propanol, N-Methyldiethanolamine ( MDEA), Triethanol amine (TEOA), Diethanolisopropylamine, Diethanolisopropanolamine (DEIPA), N,N-Dimethylisopropanolamine, 1-[Ethyl(2-hydroxyethyl)amino)]-2-propanol, Triisopropanolamine, N-(2-hydroxyethyl)-N -(2-hydroxypropyl)methylamine, 3-[2-hydroxyethyl(methyl)amino]propane-1,2-diol, 3-[ethyl(2-hydroxyethyl)amino]propane-1,2-diol, 2-(Diethylamino )propanol, 1-[methyl(propyl)amino]propan-2-ol, N,N-Diethyl-2-hydroxypropylamine, 1-(ethylmethylamino)-2-propanol, 2-(Dimethylamino)-2-methyl-1- propanol (DMAMP-80), 3-Dimethylamino-1-propanol, 4-Dimethylamino-1-butanol, 1-(dimethylamino)-2-methyl-2-propanol, 1-(Dipropylamino)-2-propanol, 2-( Buthylmethylamino)ethanol, 2-(Dipropylamino)ethanol, 2-[Methyl(2-methylpropyl)amino]ethanol, 2-[sec-Butyl(methyl)amino]ethanol, 2-(Isopropylpropylamino)Ethanol, 1-[(2- Hyd roxyethyl)propylamino]-2-propanol, 1-[Butyl(methyl)amino]propan-2-ol, N-Propyl Diethanolamine, Ethylamine, Diethylamine, Propylamine, Dipropylamine, Butylamine, Pentylamine, Hexylamine, Cyclohexylamine, N-ethyl-N -methyl-2-propanamine, diethylisopropylamine, N,N-diisopropylamine (DIPA), N-ethyl-N-methyl-1,2-ethanediamine, N,N-dimethylhexylamine, or N,N-dimethylethylamine.

In addition, the imidazole-based water-soluble agent includes, but is not limited to, 1,2-Dimethylimidazole, Imidazole, 2-methylimidazole, 1-Methylimidazole, 2-Ethylimidazole, 4(5)-Methylimidazole, 2-Ethyl-4-methylimidazole, 2 ,2′midazole), Benzimidazole, 1-Benzyl-2-methylimidazole, 2-Methyl-1-pyrroline, Pyrazole, 2-ethyl-4-ethyl imidazole, 2-methyl-4-ethyl imidazole, 1-methyl-4- ethyl imidazole, 1-methylpyrrolidine, 5-methylbenzimidazole, isoquinoline, 3,5-dimethylpyridine, 3,4-dimethylpyridine, 2,5-dimethylpyridine, 2,4-dimethylpyridine, 4-n-propylpyridine, or 2-Ethyl-4- It may be methy-1H-limidazole-1-propanenitrile.

At this time, the polyamic acid (PAA) of the aqueous phase preferably has a chemical structure represented by Chemical Formula 2 below.

<Formula 2>

2 이다. In Formula 1, n is a repeating unit and an integer from 1 to 2,500, and m is the degree of water solubility 0 < m

is 2.

In the manufacturing method according to one embodiment of the present invention, in the step of preparing the high internal phase emulsions (HIPEs), the organic solvent is a cycloalkane-based organic solvent or an alkane-based organic solvent , It may be one or more types or mixed solvents selected from the group consisting of aromatic organic solvents. More preferably, the organic solvent may be at least one selected from the group consisting of heptane, octane, cyclohexane, and o-xylene.

Afterwards, high internal phase emulsions (HIPEs) of Oil-in-water (O/w) using polyamic acid (PAA) of the aqueous phase and organic solvent of the oil phase The step of preparing is to adjust the content so that the viscosity of the aqueous solution of polyamic acid is less than a certain amount (~ 500 cP), but it is an organic solvent that is immiscible with water, cycloalkane organic solvent, alkane organic solvent, aromatic HIPE may be prepared by emulsification for 8 to 10 minutes using a homogenizer while adding at least one selected from the group consisting of organic solvents.

Then, the manufactured HIPE is placed in a mold of a desired shape and cast so that the surface is flat. After sufficiently quenching in a liquid nitrogen atmosphere (more than 5 minutes), pre-freezing sufficiently (more than 2 hours) at -40 ℃ to completely freeze HIPE to the inside, and then freeze-drying sufficiently (more than 12 hours) at -10 ℃ Polyamic acid foam is produced by removing the organic solvent, which is a continuous phase, and water, which is a dispersed phase. The dried polyamic acid foam was heated slowly in a vacuum oven at 120, 180, 250, 300, and 350 °C for 30 minutes each to thermally imidize the polyimide foam to prepare a polyimide foam.

In the manufacturing method according to one embodiment of the present invention, the thermal imidization step is preferably made in a temperature range of 120 to 350 ℃.

In the manufacturing method according to an embodiment of the present invention, in the step of forming the graphene layer, it is preferable to use a CO ₂ laser.

As a specific example, a CO2 laser cutter system (VLS2.30) having a wavelength of 10.6 μm manufactured by Universal, USA can be used, and the laser pulse duration in the above laser system is ~14 μs. As a result, the scan speed can be fixed at 3.5 inch/s, and the crystallinity of the porous graphene produced is determined by the laser power and chemical structure of the material, so it is possible to perform carbonization in various areas. A porous composite membrane having a laser carbonized graphene layer was prepared by irradiating a laser on a porous polymer material in the form of a laser beam. In the present invention, the laser power was fixed at 4.8 W and irradiated at room temperature and normal pressure.

In addition, in the present invention, the graphene layer is formed in a region having a predetermined thickness in the thickness direction of the polyimide foam by the above manufacturing method, and the light absorption rate is 97% or more in the light wavelength range of 250 to 2500 nm, or The water contact angle of the pin layer is 130 ° or more, and the water contact angle of the polyimide foam itself is 80 ° or less, providing a porous composite film having a laser carbonized graphene layer.

In addition, the present invention provides a solar-based steam generation system or seawater desalination system, characterized in that using the photothermal characteristics of the porous composite membrane prepared by the above manufacturing method. A functional membrane is floated on water, including seawater, and the graphene layer of the membrane receives sunlight and converts it into heat, while the hydrophilic polyimide foam layer in contact with water insulates the generated heat and induces the water to rise through capillarity. At this time, the raised water is converted into steam by the generated heat, and the generated steam can be collected and used as purified water.

Hereinafter, implementation examples and embodiments of the present invention will be described in detail so that those with general knowledge in the technical field to which the present application pertains can easily practice, as shown in the accompanying drawings, preferred embodiments of the present invention. In particular, the technical idea of the present invention and its core configuration and operation are not limited by this. In addition, the contents of the present invention can be implemented in various types of equipment, and is not limited to the implementation examples and examples described herein.

<Production Example 1> Production of polyimide foam

In the present invention, a polyimide foam was prepared using a polyamic acid having a chemical structure of Formula 1 below.

<Formula 1>

First, the polyamic acid of Formula 1 uses 0.2 mol of pyromellitic dianhydride (PMDA) and 0.2 mol of 4,4'-oxydianiline (ODA) in a dimethylacetamide (DMAc) solvent. condensation polymerization was performed. The solid content was adjusted to 10% by weight, the reaction was carried out in a nitrogen atmosphere using a 1L reactor, and the reaction was performed for 4 hours while maintaining low temperature conditions using an ice bath. It was confirmed that the molecular weight of the polymerized polyamic acid was 90,000 and n was 215.

Thereafter, the polymerized polyamic acid was precipitated in acetone and ground in a mixer to effectively remove the internal organic solvent. The process of obtaining the precipitate through a filter and washing with acetone was repeated three times to obtain a purified polyamic acid precipitate. Polyamic acid particles were prepared by vacuum drying at 40 °C for 12 hours or more.

Next, polyamic acid particles were put in distilled water together with a water-solubilizer (amines, imidazoles) equivalent to 2 times the amount of the prepared polyamic acid and sufficiently stirred (1 hour to 48 hours) to prepare an aqueous solution of polyamic acid.

In general, polyamic acid is very difficult to prepare in the form of an aqueous solution, but in the present invention, an aqueous solution of polyamic acid is prepared, and the water-soluble agent used in this case is 2-dimethylaminoethanol (DMEA, Aldrich) or triethylamine. (triethylamine: TEA, Aldrich) was mainly used.

It is prepared in a water-based liquid state with a concentration of 3 wt% so that the viscosity of the polyamic acid aqueous solution is 500 cP or less, and 8 High internal phase emulsions (HIPEs) were prepared by emulsification for ~10 minutes.

Then, the prepared HIPE was placed in a silicon mold and then cast to flatten the surface. After sufficiently quenching in a liquid nitrogen atmosphere (more than 5 minutes), pre-freezing sufficiently (more than 2 hours) at -40 ℃ to completely freeze HIPE to the inside, and then freeze-drying sufficiently (more than 12 hours) at -10 ℃ A polyamic acid foam was prepared by removing the organic solvent as a continuous phase and water as a dispersed phase. The dried polyamic acid foam was heated slowly in a vacuum oven at 120, 180, 250, 300, and 350 °C for 30 minutes, respectively, and thermally imidized to prepare polyimide foam.

<Preparation Example 2> Preparation of porous composite membrane

Using a CO2 laser cutter system (VLS2.30) with a wavelength of 10.6 μm manufactured by Universal, USA, the laser pulse duration was ~14 μs and the scan speed was 3.5 inch. /s, the laser power was fixed at 4.8 W, and the polyimide foam produced at room temperature and normal pressure was irradiated. A graphene layer was formed on the surface irradiated with the laser and a polyimide foam was formed on the non-irradiated surface to prepare a porous composite film.

1 schematically shows a manufacturing process of a porous composite membrane having a laser carbonized graphene layer according to an embodiment of the present invention, and a CO ₂ laser having a wavelength of 10.6 μm is irradiated to a porous polymer prepared according to an embodiment of the present invention. As a result, a porous composite membrane having a laser carbonized graphene layer composed of a porous polymer and three-dimensional porous graphene can be prepared. The porous composite membrane with the prepared laser carbonized graphene layer was prepared by combining the flexibility of the polymer and the three-dimensional structure of graphene that can withstand physical changes, resulting in a composite membrane loaded with flexibility.

<Analysis Example 1> Confirmation of crystallinity of graphene

In order to confirm the crystallinity of the three-dimensional porous graphene produced from the porous polymer according to one embodiment of the present invention, a Raman spectrometer (Reinshaw, inVia Raman Microscrope) having a laser wavelength of 514 nm was used.

Figure 2 shows the results of Raman analysis of a laser carbonized graphene layer according to an embodiment of the present invention, and three characteristic peaks of graphene have wavelengths of 1350 cm ^-1 , 1580 cm ^-1 , and 2690 cm ^-1 at It was confirmed that each represents the D, G, and 2D peaks of graphene, and it was confirmed that graphene having the same high crystallinity was formed with the intensity of the D peak compared to the low G peak.

In addition, by confirming that the full width at half maximum FWHM of the 2D peak is ~80 cm ^-1 and has one Lorentzian peak, it can be inferred that several layers of graphene are stacked irregularly.

<Analysis Example 2> Confirmation of optical properties of graphene

A UV-Vis spectrometer (Ultraviolet-visible spectrometer, Agilent, Varian Cary 5000) was used to confirm the optical properties of the three-dimensional porous graphene produced from the porous polymer.

Figure 3 shows the results of UV-Vis absorption spectroscopy of a laser carbonized graphene layer according to an embodiment of the present invention, the transmittance value (T) and the reflectance value (R) measured in the light wavelength range of 250-2500 nm are added. It is the result of calculating the light absorption amount by subtracting the value from 1.

As can be seen in FIG. 3, the three-dimensional porous graphene formed by laser carbonization absorbed more than 97% of light in all areas, which was possible in all areas due to the hexagonal structure of graphene, and the irregularly stacked 3 It can be seen that the dimensional structure enables high light absorption by increasing the specific surface area that can receive light.

<Analysis Example 3> Hydrophilicity analysis of porous composite membrane

To confirm the structural characteristics of three-dimensional porous graphene produced from porous polymers by laser carbonization, a scanning electron microscope (Hitachi, SU8230) and a surface area and porosimetry system (Micromeritics, ASAP 2020) were used. used

4 shows an electron microscope (SEM) analysis and water contact angle of a laser carbonized graphene layer and a porous polymer according to an embodiment of the present invention. As can be seen in FIG. 4, laser carbonization is performed using a porous polymer having a thickness of about 600 μm. When proceeding, it can be seen that three-dimensional porous graphene with a thickness of about 386 μm is generated on the surface, and a porous polymer layer with a thickness of about 225 μm is present.

In addition, it is confirmed that both polymer and graphene have an open pore structure suitable for application as a membrane.

In addition, when looking at the results of the water contact angle analysis, it was confirmed that the upper porous graphene layer was hydrophobic with a water contact angle of 130 ° or more due to the surface structure, and the water contact angle of the porous polymer layer of the lower polyimide foam was 80 ° or less. It was confirmed that the intrinsic hydrophilicity was maintained.

On the other hand, in the hydrophilicity of the surface of the porous composite membrane having a laser carbonized graphene layer according to the present invention, this asymmetric characteristic can have a very useful effect when applied as a membrane material used in solar-based water purification technology. The lower polymer layer of phosphorus can pull water up to the upper layer better by capillary action, and the hydrophobic graphene carbon layer present on the upper layer makes it difficult to adsorb contaminants generated during water purification, enabling effective water purification continuously. .

5 shows the results of Isotherm analysis of Ar for examining the pore characteristics and specific surface area of the laser carbonized graphene layer according to an embodiment of the present invention. The graphene layer has pores in various regions and has a large specific surface area. It is expected that it will better absorb sunlight and allow steam to form and escape.

Therefore, a porous graphene layer having a laser carbonized graphene layer composed of an upper layer of three-dimensional porous graphene having high crystallinity and excellent optical properties and a lower layer of a porous polymer having hydrophilicity and capable of dissipating heat, prepared according to an embodiment of the present invention. The composite membrane was tested for applicability to solar-based water purification technology.

<Analysis Example 4> Photothermal Characteristics Analysis of Porous Composite Membrane

First, the photothermal characteristics of the porous composite film having a laser carbonized graphene layer were analyzed as follows. According to one embodiment of the present invention, the three-dimensional porous graphene layer formed by laser carbonization has not only effective light absorption but also high photothermal properties that convert absorbed light into heat. In addition, the lower porous polymer layer is expected to be able to generate steam by allowing heat generated from graphene to be well maintained in the membrane due to its high heat dissipation characteristics.

6 is an infrared image analysis result for confirming a phenomenon in which a porous composite membrane (Janus membrane) having a laser carbonized graphene layer according to an embodiment of the present invention converts sunlight into heat. In other words, in order to confirm the photothermal characteristics of the porous composite membrane, light of 1-sun (1 kW·m ^-2 ) intensity was irradiated on the composite membrane using a solar simulator (Newport 91192-1000), and as a result, the photothermal characteristics of graphene and polymer It was confirmed that the heat dissipation characteristics of the fusion were fused and the temperature rose to more than 50 °C in just 10 minutes.

<Analysis Example 4> Analysis of vapor generation performance of porous composite membrane

Next, the vapor generation performance of the porous composite membrane having the laser carbonized graphene layer was analyzed.

FIG. 7 shows the result of quantifying the amount of water vapor generated when the porous composite membrane having a laser carbonized graphene layer according to an embodiment of the present invention converts sunlight into heat. In order to check the photovoltaic steam generation performance of the porous composite membrane, a beaker containing seawater was placed on an electronic balance, the porous composite membrane was floated on the seawater, and light at 1-sun (1 kW m ^-2 ) intensity was applied to a solar simulator (Newport 91192-1000 ), and the steam generation performance was quantified and analyzed using the following formula.

When the porous composite membrane did not exist, steam was generated at a rate of 0.45 kg·m ^-2 h ^-1 , but when the porous composite membrane was present, steam was generated at a rate of 1.34 kg·m ^-2 h ^-1 . As a result, it was confirmed that a porous composite membrane having an energy conversion efficiency (η) of 83.5% and a photovoltaic vapor generation performance was created.

<Analysis Example 4> Water Purification Performance Analysis of Porous Composite Membrane

Figure 8 shows the amount of ions when the porous composite membrane having a laser carbonized graphene layer according to an embodiment of the present invention converts sunlight into heat to purify seawater. As shown in FIG. 8, when solar-based steam purification was performed on seawater using a Janus membrane, it was confirmed that more than 99.9% of the existing ions were removed, which is lower than the standard for drinking water defined by WHO or EPO. is an ion In addition, when the above experiment was repeatedly performed, it was confirmed that the film had excellent durability as the steam generation efficiency was maintained.

Claims (10)

Oil-in-water (O/w) high internal phase emulsions (HIPEs) using polyamic acid (PAA) in aqueous phase and organic solvent in oil phase Preparing a hydrophilic porous polyimide foam having a water contact angle of 80 ° or less through freeze-drying and thermal imidization; and
A laser carbonized graphene layer comprising the step of forming a hydrophobic graphene layer having a water contact angle of 130 ° or more by irradiating a laser to one surface of the polyimide foam to carbonize a region of a predetermined thickness in the thickness direction A method for manufacturing a porous composite membrane for solar heat-based steam generation. delete The method of claim 1,
The method of manufacturing a porous composite membrane for solar-based steam generation having a laser carbonized graphene layer, characterized in that the polyimide foam is prepared from a polyamic acid having a chemical structure of Formula 1 below:
<Formula 1>

In Formula 1, n is an integer of 1 to 2,500 as a repeating unit. delete The method of claim 1,
Polyamic acid (PAA) of the aqueous phase is a method for producing a porous composite membrane for solar-based steam generation having a laser carbonized graphene layer, characterized in that it has a chemical structure of Formula 2:
<Formula 2>

In Chemical Formula 1, n is a repeating unit and an integer from 1 to 2,500, and m is the degree of water solubility, and 0 < m ≤ 2. The method of claim 1,
The organic solvent is porous for solar-based steam generation having a laser carbonized graphene layer, characterized in that at least one selected from the group consisting of cycloalkane-based organic solvents, alkane-based organic solvents, and aromatic organic solvents. A method for producing a composite membrane. The method of claim 1,
The thermal imidization method of manufacturing a porous composite membrane for solar-based steam generation having a laser carbonized graphene layer, characterized in that made in the temperature range of 120 to 350 ℃. The method of claim 1,
The step of forming the graphene layer is a method of manufacturing a porous composite film for solar-based steam generation having a laser carbonized graphene layer, characterized in that using a CO ₂ laser. Oil-in-water (O/w) high internal phase emulsions (HIPEs) using polyamic acid (PAA) in aqueous phase and organic solvent in oil phase A hydrophilic porous polyimide foam having a water contact angle of 80 ° or less prepared through freeze-drying and thermal imidization; and
A composite film comprising a hydrophobic graphene layer having a water contact angle of 130 ° or more formed by laser carbonization in a region of a predetermined thickness in the thickness direction on the upper part of the polyimide foam,
The composite film is a porous composite film for solar-based steam generation having a laser carbonized graphene layer, characterized in that the light absorption rate is 97% or more in the light wavelength range of 250 to 2500 nm. A solar-based steam generation system characterized in that using the photothermal characteristics of the porous composite membrane according to claim 9.

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