Hydrophilic 3D Interconnected Network of Bacterial Nanocellulose/ Black Titania Photothermal Foams as an Efficient Interfacial Solar Evaporator

Abstract

The design and development of scalable, efficient photothermal evaporator systems that reduce microplastic pollution are highly desirable. Herein,

a sustainable bacterial nanocellulose (BNC)-based self-floating bilayer photo- thermal foam (PTFb) is designed that eases the effective confinement of solar light

for efficient freshwater production via interfacial heating. The sandwich nanoarchitectured porous bilayer solar evaporator consists of a top solar-harvesting blackbody layer composed of broad-spectrum active black titania (BT) nanoparticles embedded in the BNC matrix and a thick bottom layer of pristine BNC for agile thermal management, the efficient wicking of bulk water, and staying afloat. A decisive advantage of the BNC network is that it enables the fabrication of a lightweight photothermal foam with reduced thermal conductivity and high wet strength. Additionally, the hydrophilic three-dimensional (3D) interconnected porous network of BNC contributes to the fast evaporation of water under ambient solar conditions with reduced vaporization enthalpy by virtue of intermediated water generated via a BNC− water interaction. The fabricated PTFb is found to yield a water evaporation efficiency of 84.3% (under 1054 W m−2

) with 4 wt % BT loading. Furthermore, scalable PTFb realized a water production rate of 1.26 L m−2 h−1 under real-time conditions. The developed eco-friendly BNC-supported BT foams could be used in applications such as solar desalination, contaminated water purification, extraction of water from moisture, etc., and thus could address one of the major present-day global concerns of drinking water scarcity.