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Gradient Vertical Channels within Aerogels Based on N‑Doped Graphene Meshes toward Efficient and Salt-Resistant Solar Evaporation
journal contribution
posted on 2020-03-19, 20:46 authored by Xiangyu Meng, Jianhui Yang, Seeram Ramakrishna, Yueming Sun, Yunqian DaiIn
the drive toward energy harvesting, graphene and their derivations
are the most promising photothermal materials for solar evaporation.
Here is a facile approach for constructing gradient vertical channels
within a ring-like three-dimensional (3D) aerogel based on porous
N-doped reduced graphene oxide (N-RGO) meshes toward interfacial water
evaporation. Intriguing gradient microchannels are constructed by
introducing a concentration gradient of NH4OH (as antifreeze)
within the N-RGO hydrogel before traditional freeze-drying. Based
on both theoretical simulation and experimental demonstrations, aerogels
with ring-like photothermal structures harvest light without angle
dependence and exhibit ring-by-ring thermal insulation and high photothermal
conversion efficiency (74.8%). Moreover, unique 3D gradient vertical
microchannels concentrate water into hot regions and achieve effective
interfacial evaporation, leading to a high evaporation rate (2.53
kg·m–2·h–1, normalized
to the evaporation area including both the top and side surface) and
solar-to-vapor conversion efficiency (90.3% and 41% higher than that
of honeycomb-like aerogels). Besides, the controllable N-doping in
terms of concentration and configurations (i.e., pyridinic and graphitic
N-dopants) greatly enhances the water transport and evaporation. The
aerogel exhibits salt resistance in highly concentrated saline water
under 5 h of cycling and also shows structural stability under the
corrosive liquid and external mechanical compression. Our work provides
attractive ways of constructing the 3D gradient ordered microstructures
by assembling graphene meshes and achieving effective thermal management
and interfacial water evaporation.