Rapid Thin-Film Evaporation with Nanoscale Transport Empowers Efficient Water–Energy Harvesting from Seawater

Harvesting freshwater and hydroenergy through evaporation from seawater simultaneously and efficiently is highly preferred for various applications but remains a challenge owing to mutually exclusive requirements: Efficient water-energy harvesting necessitates the presence of a thin water film on engineered evaporator surfaces to promote evaporation current, whereas efficient freshwater generation demands rapid bulk water transport. To decouple these originally conflicting requirements, we present a 3D modular architecture decorated with nanoscale channels that imparts rapid thin-film evaporation, enabling simultaneous and efficient cogeneration of water-electricity from seawater. The modular units endow the rapid transport of seawater in confined nanoscale channels and effective thin-film evaporation. Under 1 sun irradiation, the modular water-electricity cogenerator (MWEG) reaches a current density of 1.58 mA cm^-2, power density of 1.2 W m^-2, and high evaporation rate of 2.69 kg m^-2 h^-1. In addition, under an outdoor light concentration of up to 10 sun, the power density and evaporation rate of MWEG can be significantly increased to 4.3 W m^-2 and 27.5 kg m^-2 h^-1, respectively. These performances demonstrate the vast potential of harnessing the evaporation of Earth's seawater to address shortages of both energy and water.