Manipulating light trapping and water vaporization enthalpy via porous hybrid nanohydrogels for enhanced solar-driven interfacial water evaporation with antibacterial ability

Abstract

Aiming at improving the efficient utilization of solar energy for durable interfacial water purification, in this work, hygroscopic polyethylene imine (PEI) grafted porous MoS₂ nanoflowers were deposited on a hydrophilic mixed cellulose ester (MCE) substrate via simple vacuum filtration to build a robust porous bi-layered self-floating photothermal membrane for solar-driven interfacial water evaporation. In this membrane, the PEI-grafted MoS₂ nanoflowers in the top layer served as a 3D-porous nanohydrogel network, which enhanced light absorption via multiple reflections and realized efficient water heating via dispersed hotspots and excellent water evaporation via localizing small water clusters with low vaporization enthalpy. In the bottom layer, the MCE, as a flexible substrate with low thermal conductivity, synergistically guaranteed the good mechanical stability, the durative capillary water replenishment and the minimal heating loss. Meanwhile, this membrane exhibited photothermal synergetic anti-fouling ability provided by MoS₂ and numerous cationic PEI molecules. As a result, enhanced interfacial water evaporation (up to about 92% efficiency under 3.7 kW m⁻²) with obvious antibacterial ability and good operability and durability was achieved, making this an attractive system for clean water production.