Flexible and Salt Resistant Janus Absorbers by Electrospinning for Stable and Efficient Solar Desalination

Abstract

With recent progress in interfacial solar steam generation, direct solar desalination is considered a promising technology for providing a clean water solution through a cost effective and environmental‐friendly pathway. As a high and stable water production rate is the key to enable widespread applications, salt deposition becomes a critical issue that needs to be addressed. Herein, the authors demonstrate that a flexible Janus absorber fabricated by sequential electrospinning can enable stable and efficient solar desalination. Taking advantage of the unique structure of Janus, two functions of steam generation, solar absorption and water pumping, are decoupled into different layers, with an upper hydrophobic carbon black nanoparticles (CB) coating polymethylmethacrylate (PMMA) layer for light absorption, and a lower hydrophilic polyacrylonitrile (PAN) layer for pumping water. Therefore, salt can only be deposited in the hydrophilic PAN layer and quickly be dissolved because of continuous water pumping. Janus absorber demonstrates high efficiency (72%) and stable water output (1.3 kg m–2 h–1, over 16 days) under 1‐sun, not achieved in most previous absorbers. With a unique structure design achieved by scalable process, this flexible Janus absorber provides an efficient, stable and portable solar steam generator for direct solar desalination.

Harnessing Solar‐Driven Photothermal Effect toward the Water–Energy Nexus

“…Recently, polypyrrole (PPy) has been widely employed as the photothermal coating due to its features of black color, low-cost, and easy-tofabricate. [69,95,96] Although there are abundant modification protocols, the major concern of the abovementioned black carbon coatings is the poor adhesion to the substrates. [94] Additionally, low-cost carbon black (CB) nanoparticles and Chinese black ink are able to be uniformly deposited on the various substrates as a highly efficient solar absorber by a facile spray coating or dipcoating approach.…”

“…[95] Hence, the issue of salts accumulation on the solar absorber surface is another bottleneck for the development of solar steam generator. During practical seawater evaporation, a large number of salts will be left behind and continuously accumulate on hydrophilic solar absorbers surface after water evaporation.…”

“…[3] The according salt-rejection mechanism is probably ascribed to advection and diffusion of concentrated salt down back into the body of water, and the driving force is resulted from the increased osmotic pressure within the evaporation structure where the salt concentration exceeds the ambient ocean concentration. 2019, 6,1900883 [95] Copyright 2018, Wiley-VCH. [144] Very recently, the natural wood with millimeter-sized drilled channels and balsa wood with bimodal porous structure have been successfully demonstrated to possess excellent salt-resistant ability.…”

A Hybrid Solar Absorber–Electrocatalytic N‐Doped Carbon/Alloy/Semiconductor Electrode for Localized Photothermic Electrocatalysis

“…[10,15] The technology can achieve a solar conversion efficiency over 15%, which is highly competitive, let alone the benefits of program controllability, sustainable productivity, and system upgradability with cheaper and more efficient photovoltaic cells. [23][24][25][26][27][28] Rationally, capitalizing the full potential of solar energy, beyond the limitation of UV light excitation, that are not absorbed by photo catalyst or photovoltaic cells for water splitting will undoubtedly augment the efficiency to further accelerate technological deployment. [17][18][19][20][21][22] Despite immense efforts in designing various composition and structure to optimize the intrinsic activity of catalysts, the progress remains insufficient.…”

“…[23][24][25][26][27][28] Rationally, capitalizing the full potential of solar energy, beyond the limitation of UV light excitation, that are not absorbed by photo catalyst or photovoltaic cells for water splitting will undoubtedly augment the efficiency to further accelerate technological deployment. [23][24][25][26][27][28] Rationally, capitalizing the full potential of solar energy, beyond the limitation of UV light excitation, that are not absorbed by photo catalyst or photovoltaic cells for water splitting will undoubtedly augment the efficiency to further accelerate technological deployment.…”