The use of sunlight to drive water evaporation to obtain clean drinking water is expected to be used as an emergency method in situations such as shipwrecks or survival in the wild. Compared with the natural evaporation process and the traditional membrane separation technology, the application of a photothermal film with good photothermal conversion ability to the solar-driven water evaporation system can effectively improve the evaporation efficiency. The membrane separation and catalysis research group led by Jiang Heqing, a researcher at the Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences, used a composite strategy of different nano-carbon materials to control the microstructure of the surface of the 2D photothermal film, significantly improving the efficiency of water evaporation (J. Mater. Chem. A, 2018, 6, 963-971). On this basis, the team recently conducted further research on the hollow-cone photothermal film. Using its unique three-dimensional structure, by improving the mass and heat transfer performance of the photothermal film system, a higher light and hot water evaporation was obtained. Efficiency (J. Mater. Chem. A, 2018, 6, 9874-9881).
Inspired by the collection of sound wave auricle structure and drawing on the structure of the solar stove, Wang Yuchao and Jiang Heqing of the Membrane Separation and Catalysis Research Group designed a 3D hollow cone-shaped photothermal film with a macro size, whose photothermal conversion efficiency exceeds 93% Common 2D planar film water evaporation rate limit. Tests on the actual seawater in Jiaozhou Bay show that the 3D hollow cone photothermal film not only shows good stability, but also its evaporation efficiency is 3.5 times that of natural evaporation. During the evaporation process, the salt will be chromatographed on the conical reel and will not cover the entire photothermal film. This will not only help the enrichment and recovery of salt, but also keep the photothermal performance stable. Detailed research shows that the ultra-high photothermal evaporation performance of the 3D hollow conical photothermal film is mainly achieved through three aspects: (1) The specific geometric shape can limit the light within the conical reel, through the multi-step reflection of light, Realize the efficient absorption of sunlight by the photothermal reel, with an average absorbance of more than 99%; (2) 3D hollow conical reel does not require the use of additional thermal insulation materials to reduce heat loss into the water body, nor the use of other materials Conducting water, but by changing the height of the reel in the water, regulating the contact area with water, reducing heat loss, and realizing the ideal evaporation interface limited heating; (3) The design of the 3D photothermal cone reel structure makes The actual evaporation area is different from the irradiation area of ​​sunlight, which significantly increases the actual evaporation area. This work provides an experimental basis for the development and design of 3D photothermal film, and is expected to promote the rapid development of sunlight-driven seawater desalination technology.
The above research work was supported by the National Natural Science Foundation of China, Shandong Natural Science Foundation, and Qingdao Minsheng Science and Technology Program. Related research results were published as a cover article in Journal of Materials Chemistry A (2018, 6, 9874-9881).
Figure 1. Schematic diagram of preparation of polypyrrolyl 3D hollow cone photothermal film
Figure 2. Comparison of diffuse reflection performance (a) and absorbance comparison (b) of 3D hollow tapered film and 2D planar film samples, schematic diagram of multi-step reflection process (c)
Figure 3. The research results were selected as the key report of the cover article
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