Ningbo Materials Institute has made progress in the research of photothermal air water collection with organogel

[ Instrument network instrument research and development ] The shortage of fresh water resources is becoming more and more serious. Traditional fresh water preparation is difficult to popularize due to the large energy supply demand and the huge and complex equipment. There are water vapor resources in the earth's atmosphere (about 50,000 km3). The technology of using materials to absorb moisture in the air and implement photothermal evaporation under the action of solar energy to realize air water collection is emerging.

Tillandsia Species (Tillandsia Species) is a type of epiphytic plants whose survival does not depend on rhizomes to absorb water from the soil. The leaves can survive by directly absorbing water from the air. Under the action of the internal osmotic pressure of the leaves, the absorbed water can be transported from the outermost tissue to the internal network, and finally stored in the internal tissue system of the leaves to achieve continuous and rapid water absorption (Figure 1).

Inspired by this, Chen Tao, a researcher at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, and Xiao Peng, an associate researcher, proposed a hygroscopic photothermal organic gel (POG) to realize solar-driven photothermal air water production. The hydrophilic copolymerized polymer hydrogel network of sodium polymethacrylate/acrylamide can contain a hygroscopic organic solvent (glycerin). Similar to the Tillandsia plant, the hygroscopic glycerin medium in the POG imparts rapid water diffusion inside it under the action of osmotic pressure, and stores water inside it through the form of polymer chain swelling, realizing continuous, rapid and high-capacity POG Moisture absorption performance. Experimental proof and theoretical analysis show that the hydrophilic functional groups on the polymer network can also synergistically enhance the moisture absorption behavior of POG. At a relative humidity of 90%, the POG finally exhibited a moisture absorption performance of 6.12kg/m2 and an ultra-high equilibrium moisture adsorption of 16.01kg/m2 within 12 hours (Figure 2-3). In addition, the interpenetrating photothermal polymer network polypyrrole-dopamine (P-Py-DA) gives POG excellent photothermal performance, which can achieve controllable solar-driven interfacial moisture release to obtain adsorbed moisture (Figure 4a) -b). Outdoor experiment results show that the daily output of the POG in the actual outdoor experiment reached 2.43kg/m2, and the concentration of ions in the collected freshwater met the drinking water standards of WHO and EPA (Figure 4c-g). This research provides a new material system for solar thermal air collection. The polymer skeleton of organogel and the selection of hygroscopic media are highly designable, and the air water production performance can be further improved through design in the later period.

The related research results are titled Tillandsia-inspired Hygroscopic Photothermal Organogels for Efficient Atmospheric Water Harvesting, published in Angew. Chem. Int. Ed. (DOI:10.1002/anie.202007885). The research was funded by the National Natural Science Foundation of China, the Key Frontier Science Research Project of the Chinese Academy of Sciences, the Postdoctoral Innovative Talent Support Program, the China Postdoctoral Science Foundation, and the Wang Kuancheng International Cross Team.