A three-dimensional arched solar evaporator based on hydrophilic photothermal fibers inspired by hair for eliminating salt accumulation with desalination application

Abstract

Solar desalination has been considered a sustainable method to obtain fresh water. However, its extended application is limited by low solar evaporation efficiency, poor salt rejection and durability. Herein, inspired by the structure of hair with black colour (black hair), a three-dimensional arched solar evaporator based on hydrophilic photothermal fibers is proposed for efficient water evaporation with long-term salt rejection. The formed liquid film on the solar evaporator based on hydrophilic photothermal fibers is composed of a confined water film for water supplementation and a free-flowing water film with ultrafast directional Marangoni convection and capillary effects for eliminating salt accumulation, which function cooperatively to endow the evaporator with all-in-one function including superior solar-driven water evaporation (1.39 kg m⁻² h⁻¹, 95.1% efficiency for black hair; 1.38 kg m⁻² h⁻¹, 94.7% efficiency for model material-oxidized carbon fibers), efficient solar desalination, and long-term salt-rejection properties (continuous outdoor evaporation of seawater for 20 days) without any post-cleaning treatment. The design strategy of the solar evaporator is provided for extending the application of superhydrophilic photothermal fibers and structure-design-induced liquid film control for salt rejection in the solar desalination field.