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 photothermal
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.
