Non-Covalent Bond-Regulated Solar Evaporation Modulator: Facilitative Hydration Domains Originated via a Homogeneous Polymeric Network.

Abstract

The solar-driven evaporation technology provides a green alternative for solving water scarcity. However, it remains challenging to improve the steam conversion efficiency due to the difficulties in simultaneously coordinating light absorbance, water regulation, and thermal management for broadband solar evaporators. Here, an unconventional solar evaporative modulator material─ultra-interfacial adherent dimethyl sulfoxide polyvinyl alcohol (DMSO-PVA) hydrogel (DPH) was presented. The material is based on the regulation of the PVA-PVA intra- and PVA-water interchain hydrogen bonds by DMSO, which established an adaptive high-cross-linking and homogeneous network. The consequent ultra-thin hydrogel exploited an insulating polymer backbone and intracavity hydration domain to simultaneously improve the light absorption and thermal localization and activate the water molecule. As a proof-of-concept, under 1 sun illumination (1 kW m-2), a DPH-based graphene fiber membrane [ultra-thin hydrogel membrane (UHM)] achieved 97% light absorption, 2.33 kg m-2 h-1 water evaporation, and high salt-resistant evaporation (1.48 kg m-2 h-1 under 25 wt % brine). Compared to the pure graphene membrane, UHM increased the vaporization by 64%, decreased the heat diffusion by over 14-folds, and reduced the environmental heat loss by 2.6-folds. DPH possesses scalability and versatility in bridging nanoscale photothermal materials and solar evaporator geometric architecture and will facilitate the possibility of advanced solar thermal applications.