Solar-driven evaporation based on regulation salt crystallization behavior for high-efficiency freshwater production and salt collection

Abstract

Solar photothermal interfacial evaporation represents an approach for water purification and desalination, offering a solution to mitigate global water scarcity. However, the uncontrolled crystallization of NaCl on the evaporator surface during saline water evaporation can reduce evaporation efficiency, block water channels, and degrade the evaporator. In this study, we designed an evaporator that effectively suppresses the crystallization of NaCl (200), thereby regulating the crystal structure and shape of the precipitated NaCl. Besides, a Janus hemispherical evaporation interface was proposed, facilitating the self-shedding of NaCl under gravity. The collecting resistance ($F_{\mathrm{Cr}}$) of dendritic NaCl is reduced by about two orders of magnitude than that of cubic NaCl. Under 1 kW m⁻² illumination, the evaporator simultaneously achieved a high NaCl salt collection efficiency of 54.30 % and the evaporation rate of 1.10 kg m⁻² h⁻¹ when treating 20 wt% saltwater. This work introduces a strategy for salt resource extraction and pure water production.