Cellulose-Based Photothermal Microspheres: A Sustainable Solution to Harvesting Freshwater Outdoor

Drinking water shortage is a global issue concerning fundamental human rights and well-being, and it drives people to seek freshwater from the ocean and industrial and municipal wastewater. Herein, we propose a sustainable solution based on the photothermal cellulose hydrogel microspheres and solar interfacial evaporation to harvest freshwater. The evaporation efficiency (1 sun, 2.70 kg m-2 h-1) is substantially improved because the intermediate water in the disposable cellulose hydrogel micro-spheres can reduce the vaporization enthalpy. The abundance of cellulose on earth also makes it possible for the large-scale production and application of cellulose-based microspheres. Furthermore, a simplified water-harvesting device that can generate 4.6 kg/m2 of water daily is easily assembled with the common materials in daily life and the photothermal cellulose hydrogel microspheres. Such a low-cost device could provide a practical solution to alleviate the scarcity of drinking water in impoverished territories worldwide, which fully conforms with the sustainable development goals.