Porous and Salt-Tolerant Polyelectrolyte Hydrogels for Excellent Solar Evaporation

Hydrogels with a low evaporation enthalpy and high water-molecule activation capability are regarded as promising substrate materials for solar-driven interfacial evaporation. However, the uncontrollable porous channels and cross-linking degree of traditional hydrogels limit water mass transportation, light absorption sites, and salt reflux and therefore result in low evaporation efficiency, poor salt tolerance, and terrible operational stability. Herein, we report poly(vinyl alcohol)/carbon nanotubes-co-poly(acrylic acid)-co-poly dimethyl diallyl ammonium chloride (PVA/CNTs-co-PAA-co-PDADMAC) (PADM) polyelectrolyte hydrogels via chemical cross-linking 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 tolerance (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 days of continuous evaporation), which exhibits great advantage in solar-driven interfacial evaporation.