Interfacial solar heating by self-assembled Fe3O4@C film for steam generation

Abstract

Hydrophobic Fe₃O₄@C core–shell nanostructures are developed as the solar-thermal materials for air–water interfacial solar heating for steam generation. The Fe₃O₄@C core–shell nanostructures can self-assemble into a thin film at the air–water interface, which benefits their full utilization for light absorption and heat transfer. When needed, the Fe₃O₄@C thin film can be separated from water within 20 seconds by applying an external magnetic field. Removing the external magnetic field allows rapid reassembly of the nanostructures within a second. Such efficient separation of the light absorbers and their reformation as a thin film is beneficial to practical applications where recycling and reuse of the light absorbers are critically important. In order to evaluate their practicability for interfacial solar heating, we systematically study the water evaporation efficiency, water quality of the condensed vapor, and chemical durability of this new Fe₃O₄@C nanostructures. It is found that the water evaporation efficiency of the floating Fe₃O₄@C film can reach 1.07 kg m⁻² h⁻¹ under a solar intensity of 1 kW m⁻², which is significantly higher than the case of uniform dispersion of Fe₃O₄@C nanostructures in water.