Integrated water and thermal managements in bioinspired hierarchical mxene aerogels for highly efficient solar-powered water evaporation

Abstract

Solar-powered water evaporation is a straightforward, practical approach to use solar energy for water desalination. Solar absorbers made from photothermal materials capable of effectively confining heat and pumping water to the evaporation surface are essential for a high energy efficiency. However, separate designs of water transport routes and thermal insulating layers are required to simultaneously achieve desired water and thermal managements. This work reports an integrated design for efficient multifunctional capabilities through rational assembly of spectrally modified Ti3C2Tx (SM-Ti3C2Tx) nanosheets and polyvinyl alcohol (PVA) into a multiscale 3D aerogel with a feather-like microstructure. The aerogel contains longitudinal struts with transversely parallel ligaments developed at an angle of ≈60° from the struts, resembling the microstructure of down feathers in penguins and thus leading to excellent thermal insulation. The hydrophilic porous ligaments serve as upward water transport channels, pumping the water to the evaporation surface while confining it within the ligaments to avoid oversaturation. These functional features endow the composite aerogel with a high energy efficiency of 88.52% and an evaporation rate of 0.92 kg m−2 h−1 at a weak solar irradiance of 0.5-sun, indicating its great potential for practical solar-powered water desalination under natural sunlight.