Low‐Grade Waste Heat Enables Over 80 L m−2 h−1 Interfacial Steam Generation Based on 3D Superhydrophilic Foam

Abstract Clean water scarcity and energy shortage have become urgent global problems due to population growth and human industrial development. Low‐grade waste heat (LGWH) is a widely available and ubiquitous byproduct of human activities worldwide, which can provide effective power to address the fresh water crisis without additional energy consumption and carbon emissions. In this regard, 3D superhydrophilic polyurethane/sodium alginate (PU/SA) foam and LGWH‐driven interfacial water evaporation systems are developed, which can precipitate over 80 L m −2 h −1 steam generation from seawater and has favorable durability for purification of high salinity wastewater. The excellent water absorption ability, unobstructed water transport, and uniform thin water layer formed on 3D skeletons of PU/SA foam ensure the strong heat exchange between LGWH and fluidic water. As a result, the heat‐localized PU/SA foam enables the efficient energy utilization and ultrafast water evaporation once LGWH is introduced into PU/SA foam as heat flow. In addition, the precipitated salt on PU/SA foam can be easily removed by mechanical compression, and almost no decrease in water evaporation rate after salt precipitation and removal for many times. Meanwhile, the collected clean water has high rejection of ions of 99.6%, which meets the World Health Organization (WHO) standard of drinking water. Above all, this LGWH‐driven interfacial water evaporation system presents a promising and easily accessible solution for clean water production and water–salt separation without additional energy burden for the society.