Bioinspired photothermal polyaniline composite polyurethane sponge: Interlayer engineering for high-concentration seawater desalination

Abstract

Interfacial solar evaporation has attracted substantial research interest as an eco-friendly means of desalination. A great deal of work has been devoted to exploring broad-spectrum solar absorbers, porous floating systems, and appropriate thermal insulations. During desalination, salt accumulation may block the evaporation channel and severely decline the evaporation rate. Herein, we designed a salt-resistant solar evaporator (PANI-SPPSU@PU) based on a polyurethane sponge (PU) with the polyaniline (PANI) photothermal layer and a negatively charged sulfonated polyphenylsulfone (SPPSU) interlayer. The negatively charged interlayer appends an energy barrier, which reduces the amount of the salt ions diffusing into the interlayer and regulates the local salt concentration. By this negatively charged structure, the solar evaporator enables stable evaporation from a wide range of salinity (even saturation concentration), and achieves a high evaporation rate above 1.91 kg/m2 h in 10 wt% NaCl (at the state of the art). A promising salt-resistant mechanism via the synergy of the diffusion effect and the Donnan effect is also proposed in this work. Therefore, it provides a promising pathway for practical solar-powered high-salinity seawater desalination.