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

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. Flexible Janus absorbers enable stable and efficient solar desalination. With the absorption and water pumping layers decoupled by sequential electrospinning, the Janus membrane exhibits excellent salt‐resistance, enabling efficient (72%) steam generation and stable water output (1.3 kg m−2 h−1, 16 d) under 1‐sun. The scalable fabrication, low‐cost raw material, and stable performance make Janus a promising candidate for a portable clean water solution.