Micro-macro-capillaries fabric-based evaporator for eliminating salt accumulation and highly efficient solar steam generation

Solar steam generation is considered to be a perspective technology to address water scarcity issues globally. However, its further application is limited by the complicated preparation strategy, poor salt rejection, and durability. In this study, a novel solar steam generation system based on a three-dimensional (3D) hierarchical flax fabric (HFF) is fabricated by carbonizing and coating with polypyrrole (PPy) on the fibers surface. The HFF fabric fabricated by an ordinary loom has a 3D hierarchical structure composed of float layer (FL), basket weave layer (BWL) and plain weave layer (PWL) by an ordinary loom. The hydrophilic carbonized hierarchical flax fabric modified by PPy (CHFF-PPy) shows highly efficient water supply by the continuous water transport channels for water transportation. The formed double-scale capillary water on the surface of CHFF-PPy is composed of micro-capillary water in the yarns for high interfacial water evaporation and macro-capillary water between the yarns for salt-rejection. Therefore, these functions cooperatively to endow the CHFF-PPy with all-in -one function including superior solar-driven water evaporation (1.4 kg m- 2 h-1, 91.5 % efficiency for saline), efficient solar desalination, and long-term salt-rejecting property without any post-cleaning treatment. The design principle of the 3D fabric structures is provided for extending the application of salt rejection and the investigation of structure-design-induced double-scale capillaries control in the solar desalination field.