Leveraging Hydrophilic Hierarchical Channels to Regulate Excessive Water for High-Efficiency Solar Steam Yield.

Both the solar absorptance and water content in solar-driven interface evaporation (SDIE) devices are of equal importance for efficient solar steam yield and freshwater production, but water content regulation has garnered relatively less attention, as it is more challenging to balance the water supply rate and the evaporation rate inside SDIE devices. Herein, an SDIE device is designed by coating natural luffa with polypyrrole, which could effectively regulate the water content during the solar steam yield by its unique hydrophilic hierarchical channels to transform excessive water from the bulk state into the film state on the porous skeleton. The hierarchical channels revealed by cryoelectron microscopy experiments not only reduce the loss of heat in unevaporated water but also offer abundant escape channels for solar steam, thus enabling the proposed SDIE device to achieve an evaporation rate of 2.38 kg m h under 1 sun illumination. This work reveals the key role of hierarchical channels for water regulation in the high-efficiency solar steam yield and triggers further application of natural biomaterials with unique structures in the field of solar interfacial evaporation.