Efficient Solar-Driven Water Harvesting from Arid Air with Metal-Organic Frameworks Modified by Hygroscopic Salt.

Freshwater scarcity is a global challenge threatening human survival, especially for people living in arid regions. Sorption-based atmospheric water harvesting (AWH) is an appealing way to solve this problem. However, the state-of-the-art AWH technologies have poor water harvesting performance in arid climates owing to the low water sorption capacity of common sorbents under low humidity conditions. We report a high-performance composite sorbent for efficient water harvesting from arid air by confining hygroscopic salt in a metal-organic framework matrix (LiCl@MIL-101(Cr)). The composite sorbent shows 0.77 g g-1 water sorption capacity at 1.2 kPa vapor pressure (30 % relative humidity at 30 °C) by integrating the multi-step sorption processes of salt chemisorption, deliquescence, and solution absorption. A highly efficient AWH prototype is demonstrated with LiCl@MIL-101(Cr) that can enable the harvesting of 0.45-0.7 kg water per kilogram of material under laboratory and outdoor ambient conditions powered by natural sunlight without optical concentration and additional energy input.

A Moisture-Penetrating Humidity Pump Directly Powered by One-Sun Illumination.

There is broad demand for humidity control for industrial, commercial, and residential applications. Current humidity pumping technologies require intensive maintenance because of the complexity of their mechanical structures. Furthermore, indirect utilization of solar energy increases both cost and energy loss. Here, we demonstrate a new humidity pumping concept based on multilayer moisture permeable panels. Such panels, with a simple structure, may allow the penetration of moisture from indoor (adsorption) to outdoor (desorption) with little heat loss. One-sun illumination is introduced as the direct energy source. A proof-of-concept prototype is designed and established, successfully dehumidifying indoor air with the best dehumidification rate of 33.8 g⋅m-2⋅h-1. By applying such humidity pump, the indoor latent heat load can be handled independently, without any auxiliary unit, thus consuming no electricity.

Effect of alcohol treatment on the performance of PTB7:PC71BM bulk heterojunction solar cells.

The effect of an environmentally friendly alcohol treatment on bulk heterojunction (BHJ) polymer solar cells using the low-bandgap copolymer based on thieno[3,4-b]thiophene-alt-benzodithiophene units and [6,6]-phenyl-C71-butyric acid methyl ester is systematically investigated. Different alcohols are tested, and besides the most commonly used methanol treatment, other alcohols such as ethanol, 2-propanol, and 1-butanol also improve the device performance to certain extents as compared to the untreated solar cells. Changes of the surface structure caused by the alcohol treatment are probed with atomic force microscopy, and the modification of inner film morphology is probed by time-of-flight-grazing incidence small-angle neutron scattering (TOF-GISANS). UV/vis measurements show that the thickness of all BHJ films remains unchanged by the different solvent treatments. Thus, the enhanced device performance induced by the alcohol treatments is correlated to the reconstruction of the inner film structures probed with TOF-GISANS and the modified energy levels at the interfaces between the BHJ layer and the aluminum electrodes, evident by the enhanced short-circuit current and open-circuit voltage of the I-V curves.