Janus Nano-Micro Structure-Enabled Coupling of Photothermal Conversion, Heat Localization and Water Supply for High-Efficiency Solar-Driven Interfacial Evaporation

Photothermal conversion, heat localization and water supply are the keys to achieving efficient solar-driven interfacial evaporation. However, effective coupling between the three aspects at the air/liquid interface remains challenging. Herein, Au@Ag-Pd trimetallic nanostructure/polystyrene (PS) microsphere Janus structures are designed as the solar absorber and thermal insulator. The Janus structures deposited on a water supply layer act as a 2D interfacial solar evaporator. The PS microsphere localizes heat at micrometer scale and enhances plasmonic absorption of the Au@Ag-Pd nanocrystals supported on the microsphere. Meanwhile, the Janus structures divide the surface of water supply layer into multiple regions with sub-micrometer depths, lowering the evaporation enthalpy. Owing to the synergic effects of these components, the evaporator realizes a solar-to-vapor conversion efficiency of 99.1% and an evaporation rate of 3.04 kg m(-2) h(-1) in pure water under 1 sun illumination. The efficient solar-driven evaporation can last for over 40 h. Furthermore, the solar evaporator shows high-performance seawater desalination with salt removal ratios of near 100%. This study brings new insights for controlling evaporation thermodynamics and kinetics. The Janus nano-micro structure design can be extended to other systems for various solar-thermal applications.