Photothermal conversion materials, membrane, layer structure and applications thereof

Abstract

Present invention is related to a high performance photothermal conversion materials, membrane, layer structure and applications thereof. The said materials comprise an UV and infrared absorbed material and a visible light absorbed material with at least one of or both of these materials has photothermal conversion ability. These materials could be further produced as a porous membrane or foam layer with a plastic material. Further by layered with another hydrophilic fiber layer, a porous layer structure could be obtained by the present invention with high performance photothermal conversion, uni-direction water transportation and photocatalytic abilities. The present invention could absorb a wide range of light source (UV-to-vis-to-NIP) and convert to another energy like heat solving the insufficiency of conventional photothermal conversion material.

Description

[Technical Field]

[0001] A photothermal conversion material, particularly a material that absorbs and converts thermal energy from a broadband light source.

[0002] The ultra-efficient full-spectrum photothermal conversion material of the present invention can be applied to the field of wastewater treatment, and this application will be described in detail below. However, the present invention is not limited to this application, and any equivalent, similar or equivalent changes should be covered within the scope of the technical claims of the present invention. [Previous Technology]

[0003] With the advancement of science and technology and the development of human civilization, the world's energy consumption is increasing day by day. For example, the fossil energy contained in the earth, such as oil, natural gas and coal, will soon be exhausted due to the large-scale mining by human beings. In order to solve the energy crisis, people are committed to developing sustainable energy. Therefore, solar energy, which has the characteristics of low pollution, easy access and not easy to disappear, has become the most ideal alternative energy in the future.

[0004] In recent years, the solar energy industry has grown rapidly in terms of equipment development and technological research, and has also seen significant improvements in solar energy conversion efficiency. The most important aspect of this field is achieving high-efficiency conversion of solar energy into beneficial energy. Major manufacturers are actively investing in development, seeking methods or means to improve conversion efficiency, hoping their products will demonstrate performance exceeding expectations. However, as competition among solar photovoltaic companies intensifies, the promotion and widespread adoption of this technology is hampered by the still relatively low energy conversion efficiency and profitability, requiring a long time to recoup costs.

[0005] On the other hand, the Earth's water resources are also facing a crisis of depletion. Climate change and environmental pollution caused by population growth have greatly exacerbated the water resource predicament. In addition to the habit of saving water, how to purify and treat sewage is also a good way to alleviate the water shortage. Among them, the idea of ​​combining renewable green energy with water resource reuse through solar energy conversion technology is a perfect combination. However, how to successfully and efficiently apply solar energy conversion to water resource recycling and treatment is a major problem that needs to be solved. [Summary of the Invention]

[0006] In view of this, in order to solve the current problems of water scarcity and poor solar energy conversion efficiency, the present invention provides a super-efficient full-spectrum photothermal conversion material that can efficiently convert full-spectrum light into electrical energy, and can be applied to seawater desalination and salt production, oil fields, sewage and dye desalination and other fields.

[0007] The first inventive concept of the present invention is a high-efficiency full-spectrum photothermal conversion composite material, comprising: the group consisting of tungsten oxide, titanium oxide, copper sulfide or carbon-containing materials; and the group consisting of iron oxide, carbon nitride or noble metals.

[0008] Wherein, the tungsten oxide comprises tungsten oxide, tungsten bronze or a combination thereof.

[0009] Wherein, the tungsten oxide comprises tungsten trioxide or WO2.72 or a combination thereof, and the tungsten bronze comprises rubidium tungsten bronze or cesium tungsten bronze.

[0010] Among them, the super-efficient full-spectrum photothermal conversion composite material has photocatalytic properties.

[0011] The second inventive concept of the present invention is to process the aforementioned high-efficiency full-spectrum photothermal conversion material into an electrospun fiber membrane using an electrospun process.

[0012] The plastic used contains triacetate cellulose or polyvinylidene fluoride.

[0013] The final inventive concept of the present invention is to laminate the aforementioned electrospun fiber membrane containing the ultra-efficient full-spectrum photothermal conversion material with a hydrophilic fiber layer into a laminate.

[0014] The hydrophilic fiber layer contains polyvinyl alcohol or polyethylene terephthalate.

[0015] The present invention also includes the application of the above-mentioned high-efficiency full-spectrum photothermal conversion composite layer structure to seawater desalination or wastewater treatment.

[0016] As can be seen from the above description, the present invention has the following beneficial effects and advantages:

[0017] 1. Experiments have confirmed that the water evaporation rate of the present invention is many times higher than that of existing photoelectric conversion technology, requiring only one-third of the original wastewater treatment time, thus accelerating the water evaporation treatment speed and increasing the treatment capacity. The efficiency of seawater desalination and salt production is significantly improved, and the wastewater treatment capacity has been proven to convert hexavalent chromium into trivalent chromium.

[0018] 2. The raw materials of the present invention are low-cost and can be introduced into large-scale low-cost production and manufacturing and applied to the field of sewage treatment, or further used in the fields of seawater desalination or salt production, improving the conversion efficiency of renewable green solar energy, and providing a more favorable solution for water resource recycling and reuse.

[0019] The ultra-efficient full-spectrum photothermal material of the present invention has the ability to absorb photon energy of the full spectrum (UV-to-vis-to-NIP) wavelengths and can efficiently convert light energy directly into heat energy under light illumination, thereby improving the problem of low conversion efficiency of existing solar energy conversion which is limited to a specific wavelength range.

Implementation Method

[0021] In order to understand the technical features and practical effects of the present invention in detail, and to implement it in accordance with the contents of the specification, the preferred embodiment shown in the figure is described in detail below.

[0022] The present invention first provides a super-efficient full-spectrum photothermal conversion material, which basically includes an ultraviolet-infrared light absorbing material and a visible light absorbing material. The ultraviolet-infrared light absorbing material and / or the visible light absorbing material have the characteristic of absorbing light sources and converting them into another kind of energy, such as thermal energy.

[0023] In this invention, the ultraviolet and infrared light absorbing material is mainly tungsten oxide, titanium oxide (TiO), copper sulfide (CuS), or a carbon-containing material; the visible light absorbing material may contain iron oxide, carbon nitride, titanium oxide (TiO), copper sulfide (CuS), carbon-containing materials, or precious metals such as gold or silver. The carbon material may be graphite, graphene, or carbon nanotubes, etc.

[0024] Among them, the aforementioned titanium oxide (TiO), copper sulfide (CuS) or carbon-containing materials may already have the ability to absorb full-spectrum light, and can be compounded with other single light source absorbing materials to form composite materials to achieve more comprehensive full-spectrum absorption performance.

[0025] A preferred embodiment of the present invention comprises an ultraviolet-infrared light absorbing material, such as tungsten oxide (tungsten oxide (WOx) or tungsten bronze (MxWO3), where x may be 0.01 to 100), with a mole ratio between 1:2 and 5:1, and a visible light absorbing material, such as a composite material obtained from one or more of iron oxide (Fe3O4) or carbon nitride (g-C3N4). The tungsten oxide comprises tungsten trioxide (WO3) or WO2.72, and the tungsten bronze comprises rubidium tungsten bronze (RbxWO3, where x may be 0.01 to 100) or cesium tungsten bronze (CsxWO3, Cs0.32WO3, where x may be 0.01 to 100). This highly efficient full-spectrum photothermal conversion material can have various structural forms, including nanoparticles, nanorods, nanowires, nanobundles, nanocrystals, or urchin-like spheres.

[0026] This highly efficient full-spectrum photothermal conversion material possesses the ability to absorb photon energy across the entire spectrum (UV-to-vis-to-NIP) wavelengths and can efficiently convert light energy directly into heat energy under illumination. Furthermore, this tungsten compound contains tungsten oxide (WOx) or tungsten bronze (MxWO3) components, which possess ultraviolet, infrared, and enhanced near-infrared absorption capabilities. Tungsten bronze is MxWOX generated by doping tungsten oxide with metal elements to enhance light absorption in the solar spectrum, or strong localized surface plasmon resonance (LSPR), and intermittent charge transfer (from W6+ to W5+ oxidation states). By blending such tungsten materials with other materials, a full-spectrum photocatalytic and light absorption efficiency is achieved.

[0027] Please refer to Figures 1A and 1B. The aforementioned high-efficiency full-spectrum photothermal conversion material 111A and a suitable plastic 111B form a spinning solution with a concentration between 1 wt% and 20 wt%, more preferably between 3 wt% and 10 wt%. A composite electrospun fiber 111 is formed by an electrospinning process. Then, it is laminated on a hydrophilic fiber layer 13 composed of a hydrophilic fiber 131 to form a composite electrospun fiber layer 11. The composite electrospun fiber layer 11 and the hydrophilic fiber layer 13 form a high-efficiency full-spectrum photothermal conversion composite layer structure 10.

[0028] Preferably, the plastic 111B comprises polyvinylidene fluoride (PVDF) or cellulose triacetate (TAC), preferably a spinning liquid formed by mixing recycled cellulose triacetate (r-TAC), etc., and the composite electrospun fiber layer 11 is produced on the hydrophilic fiber layer 13 using electrospinning technology. The hydrophilic fiber layer 13 is preferably polyvinyl alcohol (PVA), modified hydrophilic polyester or polyurethane (PU), wherein the modified hydrophilic polyester comprises polyethylene terephthalate (PET) fiber nonwoven fabric.

[0029] On the other hand, the composite electrospun fiber layer 111, which is electrospun by the super-efficient full-spectrum photothermal conversion material 111A and the adapted plastic 111B, preferably has a porous fiber morphology, as shown in FIG2. The plastic 111B in the composite electrospun fiber layer 11 is used as a polymer matrix and has a hydrophobic and moisture-permeable effect. Combined with the layer structure made of the super-efficient full-spectrum photothermal conversion material 111, a combination of hydrophilic and hydrophobic materials is formed.

[0030] It is worth noting that the aforementioned electrospun fiber layer is only an example illustrating the possible applicable forms. However, in addition to forming an electrospinning solution, the ultra-efficient full-spectrum photothermal conversion material 111A and a compatible plastic 111B can also be processed by other processes, such as melt-blowing to form a porous fiber membrane layer, or by using a foaming process to form a porous foamed membrane layer, and then laminated on the hydrophilic fiber layer 13 to form the ultra-efficient full-spectrum photothermal conversion composite layer structure 10.

[0031] Please refer to Figure 3. One preferred application of the super-efficient full-spectrum photothermal conversion layer structure 10 of the present invention is for driving water evaporation. When the hydrophilic fiber layer 13 is in contact with and laid on a liquid surface W, the hydrophilic fiber layer 13 continuously absorbs water into the fibers. Then, the upper super-efficient full-spectrum photothermal conversion layer 10 contacts the light source of the external environment, such as the full-spectrum light of solar energy, to convert light energy into heat energy. The super-efficient full-spectrum photothermal conversion layer 10 generates heat, allowing water to gradually evaporate from the liquid surface W. The super-efficient full-spectrum photothermal conversion layer 10 accelerates the evaporation of water. It is worth noting that since the super-efficient full-spectrum photothermal conversion layer structure 10 provided by the present invention is a combination of hydrophilic and hydrophobic layers, after the hydrophilic layer contacts the liquid surface, the water will move unidirectionally to the hydrophobic layer and eventually dissipate, exhibiting the characteristic of unidirectional water flow.

[0032] More preferably, the unidirectional moisture-wicking properties of the ultra-efficient full-spectrum photothermal conversion composite layer structure 10 can be further achieved through the hydrophilic and hydrophobic gradients between the layers. In detail, please refer to Figure 4. When the ultra-efficient full-spectrum photothermal conversion layer 10 is used as a hydrophobic layer, the so-called hydrophobic gradient design is achieved by using several layers (three layers in Figure 4) of fibers / materials with different contact angles. Similarly, the hydrophilic fiber layer 13 uses several layers (three layers in Figure 4) with different degrees of hydrophilicity or different porosities in the material to achieve the so-called hydrophilic and hydrophobic gradient effect, as well as superior unidirectional moisture-wicking properties.

[0033] The structural engineering strategies for the ultra-efficient full-spectrum photothermal conversion layer structure 10 provided by this invention include: light absorption and light conversion into sound engineering, thermal localization and thermal conductivity, water channel design, interface engineering, biomimetic structural design, 3D evaporator design, and salt removal structure design. The main advantages are broad-band light absorption and highly efficient photothermal single or dual-component components at the light absorption point, and excellent thermal insulation and highly efficient water transport at the dielectric layer.

[0034] <Example 1>

[0035] (1) Synthesize RbxWO3-Fe3O4 nanocomposite.

[0036] 0.5952 g of WCl6 was dissolved in anhydrous ethanol with continuous stirring for 15 minutes, followed by the addition of 0.076 g of RbOH. Then, 24 mL of acetic acid was added to the mixture at 240°C, and the mixture was placed in an autoclave with a Teflon liner for 20 hours. After removing the solution from the autoclave, it was centrifuged and dried in an oven at 60°C to obtain RbxWO3.

[0037] Next, 0.2 g of the above RbxWO3 was dispersed and dissolved in 20 mL of anhydrous ethanol using ultrasound and stirred for another hour. Then, 20 mL of 0.5 moles of Fe3O4 nanoparticle ethanol solution was added to this suspension and stirred rapidly. The suspension was then centrifuged and dried in an oven at 60°C for 1 hour.

[0038] (2) Prepare RbxWO3-Fe3O4 nanocomposite electrospun fiber membrane and photothermal conversion composite layer structure.

[0039] The aforementioned RbxWO3-Fe3O4 nanocomposite was stirred and completely dissolved in 5wt% rTAC at a ratio of 9:1 (v / v) to form an electrospinning solution. The RbxWO3-Fe3O4 nanocomposite and rTAC plastic were spun onto PET hydrophilic fiber nonwoven fabric at a voltage of 15kV, a flow rate of 0.5 ml / h, and a distance of 15cm between the needle tip and the collector to obtain the super-efficient full-spectrum photothermal conversion layer structure 10.

[0040] <Example 2>

[0041] (1) Synthesize WO2.72-Fe3O4 nanocomposite.

[0042] Dissolve 0.7 g of WCl6 in 70 mL of anhydrous ethanol by stirring continuously for 15 minutes until a yellow solution is obtained. At the same time, in another container, add 0.231 g of Fe3O4 powder to 50 mL of anhydrous ethanol and stir ultrasonically to obtain a black solution.

[0043] The aforementioned yellow and black solutions were mixed and placed in a sterilizer with a Teflon liner and heated in an oven at 180°C for 24 hours. The suspension was then centrifuged and dried in an oven at 60°C for 8 hours.

[0044] (2) Preparation of WO2.72-Fe3O4 nanocomposite electrospun fiber membrane and photothermal conversion composite layer structure.

[0045] The aforementioned WO2.72-Fe3O4 nanocomposite was stirred and completely dissolved in 5wt% rTAC at a ratio of 250g to form an electrospinning solution. The WO2.72-Fe3O4 nanocomposite and rTAC plastic were spun onto PVA hydrophilic fiber nonwoven fabric at a voltage of 15kV, relative humidity of 50%, flow rate of 0.5 ml / h, and distance between needle tip and collector of 15cm to obtain the super-efficient full-spectrum photothermal conversion layer structure 10.

[0046] <Example 3>

[0047] (1) Synthesize Cs0.32-gC3N4 nanocomposite.

[0048] Dissolve gC3N4 in 40 mL of ethanol and stir for 1 hour. Then, add 0.297 g of WCl6 under vigorous stirring and mix thoroughly.

[0049] 0.065 g CsOH·H2O was added to the above suspension and stirred for 7 minutes. Then 10 mL of acetic acid was added, and the suspension was placed in a Teflon-lined sterilizer and heated in an oven at 240°C for 20 hours to carry out the reaction. After the reaction was completed, the mixture was cooled to room temperature, and the resulting product was washed four times with ethanol and then dried at 60°C for 8 hours to obtain the Cs0.32-gC3N4 nanocomposite.

[0050] (2) Prepare Cs0.32-gC3N4 nanocomposite electrospun fiber membrane and photothermal conversion composite layer structure.

[0051] The aforementioned Cs0.32-gC3N4 nanocomposite was ultrasonically mixed in a dimethylformamide (DMF) solution for 1 hour, then 2.2 g of PVDF particles were added, and the mixture was heated and stirred at 120°C for 2 hours. After cooling, it became an electrospinning solution. The electrospinning solution was then electrospun onto a PVA hydrophilic fiber nonwoven fabric to obtain the highly efficient full-spectrum photothermal conversion layer structure 10.

[0052] <Validity Test>

[0053] First, the ultra-efficient full-spectrum photothermal conversion layer structure 10 of the above three embodiments was subjected to full-spectrum light energy absorption test using a UV-VIS-NIR ultraviolet-visible-near-infrared spectrometer, as shown in Table 1 below.

[0054] Table 1, Full-spectrum light absorption capacity. Types of light Example Ultraviolet light Visible light Near-infrared light Example 1 Absorbent Absorbent Absorbent Example 2 Absorbent Absorbent Absorbent Example 3 Absorbent Absorbent Absorbent

[0055] Next, its thermal properties were tested to prove that it has the ability to heat and evaporate moisture, as shown in Table 2 below.

[0056] Table 2, thermal properties. thermal properties Example Thermal conductivity (mW / mK) Thermal diffusivity (mm) 2 / s) Thermal absorption (Ws) 1 / 2 / m2K) Thermal resistance (m 2 mK / W) Example 1 28.10 0.13 78.17 21.20 Example 2 At least 27.00 At least 0.13 At least 78.17 At least 21.20 Example 3 27.00 At least 0.13 At least 78.17 At least 21.20 Comparative example (pure rTAC membrane) 25.60 0.30 49.20 22.60

[0057] The present invention also tested the light energy and water evaporation conversion efficiency of the super-efficient full-spectrum photothermal conversion composite layer structure 10, that is, the efficiency of vapor generation at the liquid interface, as shown in Table 3 below. By laying the composite layer structure of the aforementioned embodiments on the surface of the test liquid, the results show that the present invention has a strong interface heating function. A heat zone is clearly generated at the air-water interface under the light source, and the interface water temperature gradually increases with the increase of the light source irradiation time. Such a thermal environment helps to heat the water surface and evaporate through the single-guided film structure of the present invention. Moreover, the present invention has the best photothermal conversion efficiency under solar irradiation and still has stable performance after at least several irradiation cycles. It has photostability and durability, which shows that it has the potential to be successfully introduced into the market.

[0058] Table 3, Photothermal conversion efficiency. Transformation Example Water weight loss (kg / m³) after 35 minutes of irradiation with a light source 2 ) Evaporation rate / hour (kg / m³) 2 h) Light conversion efficiency (%) Comparison of light source types for photothermal effect Number of times to reuse Example 1 1.3 3.56 89.3 Solar energy > NIR > Visible light 15 Example 2 At least 1.3 At least 3.56 At least 89.3 Solar energy > NIR > Visible light 15 Example 3 1.5 2.70 95.3 Solar energy > NIR > Visible light 12 Comparative example (water surface without any photothermal conversion structure) 0.60 1.44 -- -- --

[0059] The photothermal conversion and unidirectional characteristics of the ultra-efficient full-spectrum photothermal conversion composite layer structure 10 provided by the present invention are particularly suitable for applications in seawater desalination or desalination treatment. The salt ion content of seawater and collected condensate before and after treatment in the aforementioned embodiments is shown in Table 4 below. The present invention has the ability to treat seawater into drinking water (according to the World Health Organization (WHO) definition of salt ion content in drinking water). Therefore, the present invention does have excellent desalination ability and can produce drinking water from seawater.

[0060] Table 4. Before and after treatment Salt ion concentration Seawater before treatment Treated (drinking water) Na + 27500 ppm 3.23 ppm K + 1000 ppm 2.4 ppm Mg 2+ 5300 ppm 0.17 ppm Ca 2+ 1200 ppm 2.38 ppm

[0061] On the other hand, the ultra-efficient full-spectrum photothermal conversion composite layer structure 10 provided by the present invention also has the ability to photocatalytically decompose heavy metal components. The water treated in the above-mentioned manner contains pollutants such as nitrophenol, tetracycline, methylene blue / orange (MB / MB), and rhodamine B. The purified condensate is colorless and transparent, and the pollutant content in the water is almost zero after testing. This is because the porous membrane of the present invention has the function of adsorbing pollutants, and the ultra-efficient full-spectrum photothermal conversion material has the ability of photocatalytic conversion, which can convert organic pollutants, such as but not limited to hexavalent chromium (Cr(VI)), into non-toxic trivalent chromium (Cr(III)) and maintain them in the unidirectional membrane without flowing back into the water, thereby achieving the effect of wastewater purification.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the claims of the present invention. All other equivalent changes or modifications made without departing from the spirit disclosed in the present invention should be included in the scope of the patent application of the present invention. [Simplified Explanation of the Diagram]

[0020] Figures 1A and 1B are schematic diagrams and partial enlarged views of a preferred embodiment of the high-efficiency full-spectrum photothermal conversion composite layer structure of the present invention. Figure 2 shows the porous fiber morphology of the composite electrospun fiber layer of the present invention. Figure 3 is a schematic diagram of the application of the high-efficiency full-spectrum photothermal conversion composite layer structure of the present invention to liquid surface treatment. Figure 4 is a schematic diagram of a preferred embodiment of the hydrophobic gradient structure design of the high-efficiency full-spectrum photothermal conversion composite layer structure of the present invention.

Claims

1. A high-efficiency full-spectrum photothermal conversion composite material, comprising composite materials randomly compounded from the following two groups: the group consisting of tungsten oxide, titanium oxide, copper sulfide or carbon-containing materials; and the group consisting of iron oxide, carbon nitride or noble metals.

2. The high-efficiency full-spectrum photothermal conversion composite material as described in claim 1, wherein: The tungsten oxide includes tungsten oxide, tungsten bronze, or a combination thereof, the carbon-containing material includes graphite, graphene, or carbon nanotubes, and the precious metal includes gold or silver.

3. The high-efficiency full-spectrum photothermal conversion composite material as described in claim 2, wherein: The tungsten oxide comprises tungsten trioxide or WO2.72 or a combination thereof, and the tungsten bronze comprises rubidium tungsten bronze or cesium tungsten bronze.

4. The high-efficiency full-spectrum photothermal conversion composite material as described in claim 1 or 2, wherein, This high-efficiency full-spectrum photothermal conversion composite material exhibits photocatalytic properties.

5. A high-efficiency full-spectrum photothermal conversion composite film layer, comprising the high-efficiency full-spectrum photothermal conversion composite material as claimed in claims 1, 2, 3 or 4, and a porous fiber film layer or a porous foamed film layer obtained from a plastic.

6. The high-efficiency full-spectrum photothermal conversion composite film layer as described in claim 5, wherein, The plastic contains triacetate cellulose or polyvinylidene fluoride.

7. A high-efficiency full-spectrum photothermal conversion composite layer structure comprising, stacked on each other: a high-efficiency full-spectrum photothermal conversion composite material film layer, comprising the high-efficiency full-spectrum photothermal conversion composite material as claimed in claims 1, 2, 3 or 4, and a porous fiber film layer or a porous foamed film layer obtained from plastic; and a hydrophilic fiber layer.

8. The photothermal conversion fiber layer structure as described in claim 7, wherein: The hydrophilic fiber layer comprises polyvinyl alcohol, modified hydrophilic polyester, or polyurethane, wherein the modified hydrophilic resin comprises polyethylene terephthalate.

9. The photothermal conversion fiber layer structure as claimed in claim 7 or 8, wherein: The high-efficiency full-spectrum photothermal conversion composite material film layer and / or hydrophilic fiber layer have material properties or structures with hydrophobic and hydrophilic gradients, respectively.

10. A super-efficient full-spectrum photothermal conversion composite layer structure for wastewater treatment, seawater desalination, or desalination, comprising the super-efficient full-spectrum photothermal conversion composite layer structure as described in claim 7 or 8.

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