Bio-inspired magnetically induced self-assembling Janus solar evaporator with antifouling and antiscaling properties

Abstract

Engineering solar evaporators with Janus structures is crucial for facilitating water transition and heat localization to enhance water evaporation efficiency. However, the fragile discontinuous bilayer structures and unavoidable surface fouling significantly hinder their application. Herein, inspired by the Janus structure of Black Amanita mushrooms, we designed a robust solar evaporator with an integrated wood-like and Janus structure using directional freeze-casting and magnetically induced self-assembly of polypyrrole-coated Fe₃O₄ particles as a build-in photothermal top layer within a hydrophilic matrix, followed by covering it with an additional hydrophobic fluorine layer to simultaneously regulate surface wettability and antifouling properties. Incorporating the hydrophobic fluorine layer onto the solar evaporator not only enhances its water evaporation efficiency via thermal localization effects, but also prevents fouling, salt, and dust scaling accumulation on its surface, facilitating water transportation, thus achieving a groundbreaking performance with the evaporation rate of 2.13 kg m⁻²h⁻¹ under one sun irradiation. Moreover, the mechanical performance of the as-prepared solar evaporator can be further optimized by precisely modulating supramolecular interactions within its structure, achieving Young’s modulus over 4 MPa and maintaining structural integrity after the peel-off tests. The fabricated solar evaporator enables highly efficient water purification from artificial seawater, oil-in-water emulsions, and industrial wastewater, providing a rational strategy for designing high-yield solar evaporation systems for wastewater containing complex contaminants