阅读说明：本技术 一种光热转换薄膜及其制备方法和用于太阳能蒸汽产生的双层蒸发结构 (Photo-thermal conversion film, preparation method thereof and double-layer evaporation structure for solar steam generation ) 是由 王成兵 许珂圆 李政通 王九龙 于 2019-10-22 设计创作，主要内容包括：本发明提供一种高性能泡沫金属基光热转换薄膜及其制备方法和用于太阳能蒸汽产生的双层蒸发结构,高性能泡沫金属基光热转换薄膜为CuO@CF和CuO/Ag@CF光热转换薄膜,将CuO@CF或CuO/Ag@CF光热转换薄膜与三聚氰胺泡沫形成双层蒸发结构,用于太阳能蒸汽产生,减少了在单层蒸发系统中发生的从太阳能吸收器到下面的水体的向下传导热损失,进一步提高了蒸发效率。且本发明采用CuO/Ag@CF光热转换薄膜较于传统纯贵金属材料薄膜具有更低的成本。(The invention provides a high-performance foam metal-based photothermal conversion film, a preparation method thereof and a double-layer evaporation structure for solar steam generation. Compared with the traditional pure noble metal material film, the CuO/Ag @ CF photo-thermal conversion film has lower cost.)

1. A preparation method of a CuO @ CF photothermal conversion film is characterized by comprising the following steps:

step 1, Cu (OH)₂Preparation of films

Preparation of NaOH and (Na)₂S₂O₈Soaking the foamy copper in the mixed solution, taking out after standing reaction, washing and drying to obtain Cu (OH)₂@CF；

Step 2, preparation of copper oxide film

Mixing Cu (OH)₂And @ CF is subjected to heat treatment to form a layer of copper oxide film on the surface of the foam copper, so that the CuO @ CF photothermal conversion film is obtained.

2. The method of claim 1, wherein in step 1, the concentration of NaOH in the mixed solution is 0.8-1.2mol L^-1，(Na)₂S₂O₈The concentration of (A) is 0.03-0.08mol L^-1。

3. The method of preparing a CuO @ CF photothermal conversion film according to claim 1, wherein in step 1, the thickness of the copper foam is 1 to 1.5 mm.

4. The method for preparing a CuO @ CF photothermal conversion film according to claim 1, wherein the standing reaction in step 1 is specifically a standing reaction at room temperature for 4 to 6 hours.

5. The method of claim 1, wherein the heat treatment temperature is 150 ℃ and 210 ℃ for 1-3 hours.

6. The CuO @ CF photothermal conversion film produced by the production method according to any one of claims 1 to 5.

7. A CuO/Ag @ CF photothermal conversion film, wherein the CuO film of the CuO @ CF photothermal conversion film according to claim 6 is covered with an Ag film.

8. The CuO/Ag @ CF photothermal conversion film according to claim 7, wherein the Ag film thickness is 4 to 6 nm.

9. The method of manufacturing a CuO/Ag @ CF photothermal conversion film according to claim 7 or 8, wherein an Ag film is vacuum-deposited on the CuO film of the CuO @ CF photothermal conversion film according to claim 6.

10. A double-layer evaporation structure for solar steam generation is characterized by comprising an upper layer and a lower layer which are combined together, wherein the upper layer is a light-heat conversion film, and the lower layer is melamine foam; the CuO @ CF photothermal conversion film described in claim 6 or the CuO/Ag @ CF photothermal conversion film described in claim 7 or 8.

Technical Field

The invention relates to the field of photo-thermal materials, in particular to a high-performance foam metal-based photo-thermal conversion film, a preparation method thereof and a double-layer evaporation structure for solar steam generation.

Background

The photo-thermal material is used as the key of high-efficiency photo-thermal conversion and is also the core of the solar steam technology. The heat generated by photothermal materials can be used to drive the generation of steam, which has attracted extensive and intensive research due to its great potential for cost-effective and environmentally friendly water purification.

Current technology for producing steam using solar energy relies on the absorption of solar radiation at the surface of the material and the transfer of the accumulated heat to bulk water either directly or indirectly through an intermediate heat transfer fluid because of high light losses, large surface heat losses, or the need for vacuum to reduce convective heat losses, which increases the cost and complexity of the photothermal system. Therefore, there is a strong need to develop cost-effective and efficient solar energy collection systems. Low cost micro/nano structured photothermal systems have recently attracted considerable attention. Nevertheless, an attractive important problem is that the nanoparticles in this case are wasted by absorbing and scattering the incident light. To overcome this problem, a number of approaches have emerged. Such as absorbers using various black materials (e.g., porous carbon materials), but since the carbon-based material has a high reflectance, a metal plasmon structure and semiconductor nanoparticles have appeared, which have been proved to absorb solar energy more efficiently. However, the metal particles such as Ag, Pt, Au and Pd, which are developed at present as absorbers, are not only expensive, but also use a large amount of them, which results in an excessively high cost.

The substrate used for thermal positioning acts as a thermal insulator, reducing heat transfer between the vaporization region and the bulk liquid. There are currently commercial polystyrene foams used as the underlying substrate, which are closed cell hydrophobic foams, as the float and thermal insulation layer, further reducing the downward heat conduction loss. The biggest problem with this design is that it may limit the optical losses of the incident sunlight, resulting in a reduction in the input energy. There is still a great challenge to convert solar radiation into heat energy for utilization.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a high-performance foam metal-based photothermal conversion film, a preparation method thereof and a double-layer evaporation structure for solar steam generation, so that the downward conduction heat loss from a solar absorber to the lower water body in a single-layer evaporation system is reduced, and the evaporation efficiency is further improved. Compared with the traditional pure noble metal material film, the CuO/Ag @ CF photo-thermal conversion film has lower cost.

The invention is realized by the following technical scheme:

a preparation method of a CuO @ CF photothermal conversion film comprises the following steps:

step 1, Cu (OH)₂Preparation of films

Preparation of NaOH and (Na)₂S₂O₈Soaking the foamy copper in the mixed solution, taking out after standing reaction, washing and drying to obtain Cu (OH)₂@CF；

Step 2, preparation of copper oxide film

Mixing Cu (OH)₂And @ CF is subjected to heat treatment to form a layer of copper oxide film on the surface of the foam copper, so that the CuO @ CF photothermal conversion film is obtained.

Preferably, in step 1, the concentration of NaOH in the mixed solution is 0.8-1.2mol L^-1，(Na)₂S₂O₈The concentration of (A) is 0.03-0.08mol L^-1。

Preferably, in step 1, the thickness of the copper foam is 1-1.5 mm.

Preferably, in the step 1, the standing reaction is specifically at room temperature for 4-6 h.

Preferably, in step 2, the temperature of the heat treatment is 150 ℃ to 210 ℃ for 1 to 3 hours.

The CuO @ CF photo-thermal conversion film prepared by the preparation method.

A CuO/Ag @ CF photo-thermal conversion film is characterized in that a layer of Ag film covers the CuO film of the CuO @ CF photo-thermal conversion film.

Preferably, the Ag film thickness is 4-6 nm.

The preparation method of the CuO/Ag @ CF photothermal conversion film is characterized in that an Ag film is evaporated on the CuO film of the CuO @ CF photothermal conversion film in vacuum.

A double-layer evaporation structure for solar steam generation comprises an upper layer and a lower layer which are combined together, wherein the upper layer is a light-heat conversion film, and the lower layer is melamine foam; the photo-thermal conversion film is the CuO @ CF photo-thermal conversion film, or the CuO/Ag @ CF photo-thermal conversion film.

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

the copper oxide film is prepared on the surface of the foam copper through an in-situ chemical reaction, and the result shows that a compact CuO tree-shaped nanowire structure grows on the surface of the foam copper, meanwhile, the CuO tree-shaped nanowire is covered by a layer of CuO nanoflower, each nanoflower is in a flower-shaped sphere shape and is formed by tightly inlaying a plurality of nanosheets with layered petal-shaped structures, and the light absorption area is greatly increased. CuO is black, and can better absorb sunlight, and copper has excellent thermal conductivity, which makes CuO @ CF have excellent light absorption and steam generation properties.

The invention also adds a layer of silver film on the CuO @ CF, and experimental results show that the light absorption of the silver-plated CuO/Ag @ CF photothermal conversion film is obviously higher than that of the CuO @ CF film, because the plasmon effect of the silver-plated noble metal particles Ag enhances the light absorption, which is attributed to the surface-activated plasmon effect of the noble metal particles. Ag nano-particles with different particle sizes are deposited on the surface of CuO, so that the optical absorption wave band is widened. The silver-plated CuO/Ag @ CF photo-thermal conversion film shows excellent light absorption performance, wherein the average light absorption efficiency is 87.27%, and the high light absorption ensures the high-efficiency conversion capability of the photo-thermal material. The net evaporation rate of CuO/Ag @ CF is higher than that of CuO @ CF, and under the condition of primary solar radiation, the net evaporation rate of CuO/Ag @ CF can reach 1.0976kg m^-1h^-1The highest evaporation efficiency of solar heat can reach 78%.

The photo-thermal conversion film and the melamine foam form a double-layer evaporation structure, the surface of the melamine foam is of a framework structure connected by a three-dimensional porous net, and compared with the traditional polyethylene and polystyrene foam, the melamine foam has the characteristics of higher elasticity, low cost and stable mechanical property, and meanwhile, the inherent porous structure and super-hydrophilic property of the melamine foam enable the melamine foam to continuously transport water at the bottom to a gas-liquid interface through capillary force. The CuO/Ag @ CF is placed on the melamine foam, the interface connection is good, and the film is an ideal barrier-free water channel, so that the photo-thermal conversion film can timely supplement seawater to a reaction interface while water vapor is generated. On the other hand, compared with polystyrene foam, the melamine foam has lower thermal conductivity, can effectively reduce heat conduction loss, avoids heat from being greatly dissipated into water, and forms effective localized heating, thereby improving the generation of solar steam.

Drawings

FIG. 1 is a change in appearance color during the preparation of the CuO @ CF photothermal conversion film prepared in example 1;

FIG. 2 is a microstructure of the CuO @ CF photothermal conversion film prepared in example 1;

FIG. 3 is a microscopic topography of a melamine foam surface;

FIG. 4 is an X-ray diffraction pattern of a CuO film prepared by an in situ reaction on copper foam of example 1;

FIG. 5 is an infrared image of the CuO @ CF and melamine foam bilayer structure of example 1 on water;

FIG. 6 is a reflection spectrum of a copper foam-based composite photothermal material.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

Preparation of CuO/Ag @ CF composite film

1. Cleaning treatment of Copper Foam (CF)

Selecting commercial foamy copper, placing the foamy copper into dilute hydrochloric acid with the mass fraction of 3%, ultrasonically cleaning for 5-10 min at the power of 50-70W, taking out the foamy copper, and washing with deionized water until the foamy copper is clean. Then respectively ultrasonically cleaning the mixture in absolute ethyl alcohol and deionized water for 5-10 min by the same method. Thereby removing impurities, oxides/hydroxides, grease and the like on the surface of the copper foam. And taking out to obtain clean foamy copper.

2. Preparation of Cu (OH)₂Film(s)

Preparation of NaOH and (Na)₂S₂O₈And stirring the mixed solution by using a magnetic stirrer until the mixed solution is uniform. The copper foam was then soaked vertically in the beaker walls of the mixed solution. Standing at room temperature for 5h, taking out, and covering a layer of light blue film on the surface of the foam copper. The obtained sample was repeatedly washed with deionized water and absolute ethanol, and dried in air. Preparing a blue copper hydroxide film on the surface of the foam copper to obtain Cu (OH)₂@CF。

3. Preparation of copper oxide film

Mixing Cu (OH)₂And annealing @ CF at 180 ℃ for 2 hours, and then slowly cooling the product to room temperature along with the furnace to obtain a copper oxide film growing on the surface of the foamy copper, namely the CuO @ CF photothermal conversion film.

4. Vacuum coating

Vacuum evaporating a noble metal film with the thickness of 5nm on the copper oxide film of the CuO @ CF photothermal conversion film by using evaporation coating equipment ZDF-5277: and putting the CuO @ CF photothermal conversion film into a vacuum chamber, turning on a power supply to pump the vacuum chamber to a vacuum state, turning on a metal evaporation power supply, setting the evaporation thickness to be 5nm, and evaporating metal silver to the surface of the copper oxide film at high temperature to form a uniform Ag film with the thickness of 5nm to obtain the CuO/Ag @ CF photothermal conversion film.

Second, generation of solar steam

The sunlight is simulated by utilizing a xenon lamp parallel light source, and the sunlight intensity is measured by an optical power meter. The intensity of the simulated sunlight is quantitatively adjusted by adjusting the size of the working current of the xenon lamp parallel light source, the size of a light spot (an optical filter) and the height from an evaporation interface to the linear height of the simulated light device. The mass change is recorded by combining an electronic microbalance with a notebook computer, a solar evaporation experiment platform is constructed, the evaporation efficiency of saline water and the photothermal conversion efficiency of a sample film under the experiment condition can be obtained through analysis and calculation, and the photothermal performance research is carried out.

The platform comprises a temperature and humidity measurement and adjustment system, an optical simulation test system and a quality change test system. Optical simulation test system: the simulation equipment of sunlight adopts a xenon lamp light source (CEL-HXF300) of a Miao gold source as a high-light-power full-waveband light source, and has a spectrum similar to that of the sunlight. The light energy output is centralized and stable, and the light utilization in the test is convenient. The optical power meter (CEL-NP2000) of Miao gold source was used for measuring the solar light density by arranging filters (CEL-AB50) and (CEL-AM1.5) and adjusting the intensity of the solar light to the experimentally set intensity.

Temperature humidity measurement governing system: surface temperature measurements were taken by an equipped infrared camera (Fotric222 s); the detection and the regulation of the ambient temperature and the ambient humidity are realized through a temperature and humidity alarm (YD-HT), an air conditioner remote controller (AIRC800), a grid air conditioner (ENJOYWIND) and a semiconductor dehumidifier (MD-16E).

Quality change test system: measuring the mass change of the simulated seawater and the photo-thermal material under simulated illumination, placing the beaker carrying the samples on an electronic microbalance (Aohaus AR224CN) with the precision of 0.0001g, starting related instruments and test software, and automatically transmitting and recording the data change to a notebook computer.

In order to simulate the seawater environment, brine with the concentration of 3.5 wt% is prepared, and a photothermal evaporation desalination experiment is carried out. At the same time, a floating insulation material melamine foam of the same size as the sample was prepared. The melamine foam with the thickness of 1cm is used as a lower layer, the melamine foam is responsible for transporting water and supporting, and the thin film material on the upper layer is used for heating and evaporating brine at the interface in a thermal positioning mode, so that steam can be generated efficiently. Meanwhile, the exterior of the beaker is wrapped by a foam board with the thickness of 1cm, so that heat is prevented from being dissipated from the side surface of the beaker.

The amount of change in brine mass was measured under different thickness sample conditions. The salt water evaporation rate was measured by the test software every 3min under stable conditions and the data was recorded for 60min, with each group being tested 3 times.

Finally, the evaporation rate of the device in dark field was also tested and subtracted from all the evaporation rates measured under irradiation to eliminate the effect of natural water evaporation.

Pouring a proper amount of 3.5 wt% saline water into a beakerThe double-layer evaporation structure formed by the CuO @ CF and the melamine foam is put into the saline water, and the system can realize self-floating, so that the sample is not sunk in the saline water. And putting all the devices on a precision electronic balance integrally, and monitoring the mass change caused by water evaporation on line in real time. Under 1-3 suns (1kW m)^-2) And carrying out a solar steam generation test. Then, the sample CuO/Ag @ CF is tested, and the specific flow is the same as above.

At the same time, the same beaker was filled with the same amount of brine, and the evaporation test was performed only on the brine in the dark field without any sample.