High-performance solar-driven interfacial evaporation through molecular design of antibacterial, biomass-derived hydrogels

Hydrogel has been regarded as one of the most promising candidates for next-generation solar evaporation technology to produce freshwater from non-potable water. However, synthesizing hydrogel absorbers that can precisely regulate water state and significantly reduce the water vaporization enthalpy remains a grand challenge. Herein, we report the rational design of a novel hydrogel hybrid solar evaporator constructed by poly(vinyl alcohol) and sodium lignosulfonate (SLS), with addition of carbon nanotube as a light absorption material. The abundant sulfonate and hydroxyl groups of SLS enhance the interplay between hydrogel and water molecule through electrostatic interaction and hydrogen bond. As such, the presence of SLS not only remarkably promotes the hydrophilicity and water transport of hydrogel, but also precisely tunes the state of water molecule and the content of intermediate water for reducing the water vaporization enthalpy. The combined advantageous features endow the as-prepared hydrogel with an evaporation rate up to 2.09 kg m-2 h-1 under 1 Sun illumination, along with good anti-acid/basic abilities, antibacterial property, high salt-tolerance, and self-cleaning capability in purifying different types of wastewater. Finally, an outdoor solar seawater desalination device is designed to generate drinking water from seawater. The daily drinking water production amount per square meter is ca. 13 kg, which satifies the five adults' daily water consumption (12.5 kg). The present study highlights that rationally constructing the molecular architecture of hydrogel and tuning the interplay between water and hydrogel are effective strategies to fabricate advanced hydrogel solar evaporators for addressing the global freshwater shortage.