Dendritic Structure-Inspired Coating Strategy for Stable and Efficient Solar Evaporation of Salinity Brine

Abstract

Solar thermal evaporation has been widely used to tackle the problem of freshwater shortage. The strategy to improve the evaporative performance of solar thermal evaporation by simple and effective methods is still a challenge. Herein, a dendritic structure-inspired coating strategy based on the dendritic structure of polyvinyl alcohol (PVA) colloids firmly grabbing titanium trioxide (Ti2O3) on the outer surface as a light-absorbing core–shell filler was prepared using the non-solvo-induced precipitation method. Such a core–shell structure was then coated on the PVA sponge to prepare the solar photothermal composite Ti2O3/PVA@PVA, which gave full play to the photothermal advantage of the filler itself and can be long-term stable. Meanwhile, a three-dimensional Ti2O3/PVA@PVA evaporator with an embossment-sawtooth structure was prepared, which enhances light absorption to 98% in the whole solar spectrum through folds. Under 1.0 solar irradiation, the evaporation rate reaches as high as 2.66 kg m–2 h–1 and the evaporator illustrates good stability in simulated seawater for 7 consecutive days. Such a design showed good salt resistance and self-cleaning ability and could be reliably used for seawater desalination. In addition, the evaporator illustrates good adsorption capacity for dye molecules and heavy metal ions. This work provides new insights into the development of simple, efficient, environmentally friendly, sustainable, and salt-resistant solar evaporators.