Porous and Salt-Tolerant Polyelectrolyte Hydrogels for Robust Solar Evaporation

Abstract

Hydrogels with low evaporation enthaply and high water-molecule activation capability are regarded as promising substrate materials for solar-driven interfacial evaporation.However, the uncontrollabe porous channels and cross-linking degree of traditional hydrogels limit water mass transportation, light absorpotion sites and salt reflux, and therefore result in low evaporation efficiency, poor salt-tolerant property and terrible operational stability. Herein, we report a polyvinyl alcohol/carbon nanotubes-co-polyacrylic acid-co-poly dimethyl diallyl ammonium chloride (PVA/CNTs-co-PAA-co-PDADMAC) (PADM) polyelectrolyte hydrogels via chemical crosslinking and polymerizing strategy. The as-prepared polyelectrolyte hydrogels possess interconnected porous channels (abundant porosity of 76.24%, high total pore area of 0.99 m2 g-1, large average pore diameter of 18.79 μm) and controllable cross-linking degree (good mechanical property), which can greatly promote the water mass transportation (0.395 g min-1), light absorption sites and salt reflux. As a result, the PADM polyelectrolyte hydrogels can maintain high evaporation rate of 3.58 kg m-2 h-1, excellent salt-tolerant property (evaporation rate of 3.18 kg m-2 h-1 under 20 wt% high-concentration brine) and superior operational stability (invariable evaporation rate after 8-day continuous evaporation), which exhibits great advantages in solar-driven interfacial evaporation.

Keywords: polyelectrolyte hydrogels, porous channels, salt-tolerant property, mechanical flexibility, solar evaporation