Bioinspired porous spindle-knotted sponge evaporator prepared with a chemically reactive ink coating for efficient solar desalination

Abstract

The multi-scale structural design of solar evaporators was considered one of the methods to improve the photothermal performance by enhancing light absorption and optimizing the water transport pathways. Nonetheless, development of simple and effective technologies to regulate the structure of evaporators remain challenging. In this study, we developed a bioinspired robust porous spindle-knotted solar evaporator by directly spraying a layer of ink-containing polyethyleneimine-pentaerythritol pentaacrylate (BPEI-5Acl) reactive coating onto a hydrophilic melamine sponge (MS). Additionally, the reactive coating exhibits secondary reactive properties, enabling it to further react with octadecylamine (ODA) to effectively adjust the surface microstructure and wettability, forming a three-dimensional core–shell structure with hydrophilic interior and hydrophobic exterior. Benefiting from the porous spindle-knotted microstructure, the evaporator achieves a light absorption rate exceeding 93 %. Coupled with its inner hydrophilic and outer hydrophobic properties, the evaporator achieves an evaporation rate of 2.04 kg m^-2h⁻¹ and the conversion efficiency of 94.7 %. Furthermore, the reactive coating on the surface of the evaporator has robust adhesion with the ink, effectively achieving durability in desalination and removal of heavy metals and dyes during the evaporation process. This simple and effective reactive coating strategy provides a model for the large-scale production of solar evaporators.