Cuttlebone‐Derived Interfacial Solar Evaporators for Long‐Term Desalination and Water Harvesting

Abstract Interfacial solar‐vapor generation is very promising for obtaining freshwater, but suffers from serious evaporation rate degradation due to salt‐fouling and low freshwater collection rate under natural sunlight. Here, cuttlebone‐derived solar evaporators for long‐term desalination and water harvesting are reported. The solar evaporators are prepared by modifying the cuttlebone in turn with polydopamine, reduced graphene oxide, and polypyrrole as the photothermal composite. The solar evaporator shows i) excellent photothermal effect owing to a synergistic effect between the photothermal composite and its hierarchical micro‐/nanostructure, and ii) stable evaporation rate and good salt resistance even during the evaporation of concentrated brines (3.5–20 wt%) because of ultrafast water transport in the superhydrophilic 3D directional channels. The ultrafast water transport guarantees sufficient water supply, automatic very fast salt exchange, and a decline in salt concentration gradient. The transverse and longitudinal water streaming allows the increased salt concentration or even the temporarily deposited salt in/on the evaporator to be transferred back to the bulk brine in time. Consequently, 8.32 kg m⁻² of freshwater is collected in 10 h solar desalination under weak natural sunlight, which is adequate for the daily drinking water demand of several people.