In Situ Synthesis of Self-Floating Janus Fe<sub>3</sub>O<sub>4</sub>@IF Evaporator for Solar-Driven Interfacial Evaporation

Solar‐driven interfacial evaporation is one of the most promising technologies to address global freshwater shortages. Compared with the integrated structure, monolithic system with asymmetric wettability can be used alone to reduce the structural complexity without sacrificing the localized management of heat. Herein, a monolithic structure of Janus Fe3O4@IF evaporator with asymmetric wettability has been fabricated via a simple in situ hydrothermal method. The low‐cost Janus Fe3O4@IF evaporator can be self‐floating with a sizable surface area, high porosity, and low density, which presents excellent light absorption features of 98.1% within a broadband wavelength range of 200–2500 nm. Due to the strong capillarity action and Janus wettability, the evaporation is efficient (1.64 kg m−2 h−1) and stable even treating with highly concentrated brine of 20 wt%. This work demonstrates an effective strategy for achieving high‐performance solar‐driven interfacial evaporation and superior salt rejection capability, which can be potentially utilized in seawater desalination.