Design of a Pyrrole/Polyimide fiber-based Janus aerogel to suppress salt deposition and enhance solar steam generation performance

Abstract

The emerging solar steam generation shows great potential to alleviate the global freshwater crisis. The efficacy of evaporators and salt deposition are two crucial parameters for water transportation and desalination stability. Here we designed a Janus Polypyrrole/Polyimide fiber-based aerogel via electrospinning, unidirectional freezing, and in-situ polymerization with a hydrophobic upper layer and a hydrophilic bottom layer. The bottom of the columnar aerogel was a hydrophilic Polypyrrole/Polyimide fiber-based aerogel to ensure continuous upward transport of water, while the upper hydrophobic surface, was made of a CNT composite layer, for light absorption, heat generation, and insulation. Under 1 kW m−2 solar illumination, the Janus aerogel showed a rapid water evaporation rate of 2.43 kg m−2 h−1 and a high solar-to-vapor efficiency using a 3.5 wt% NaCl solution. Owing to the Janus structure, the aerogel can achieve efficient light-thermal conversion performance and excellent resistance to salt deposition. Furthermore, after 12 h of continuous testing in 20 wt% NaCl, salt crystals were deposited only at the edges of Janus aerogel. The water desalinated from simulated seawater and heavy metal ions solution met the World Health Organization's standard. The rational design enhancing evaporation performance makes the evaporator a promising device for stable and continuous solar desalination.