Highly efficient three-dimensional solar evaporator for high salinity desalination by localized crystallization

TLDR

Solar‑driven water evaporation is an environmentally benign method for water purification and desalination, but its efficiency is limited by salt concentration and accumulation. The study proposes an energy‑reutilizing strategy based on a bio‑mimetic 3D structure. The design uses a spontaneously formed water film with thickness inhomogeneity and temperature gradient that fully utilizes input energy via the Marangoni effect, leading to localized salt crystallization. Solar‑driven evaporation achieved 2.63 kg m⁻² h⁻¹ and >96 % energy efficiency under one sun at 25 wt % NaCl, with a water collection rate of 1.72 kg m⁻² h⁻¹; the crystallized salt remains on the evaporator and can be easily removed, and neither energy efficiency nor evaporation rate is affected by salt accumulation, indicating sustainable practical application.

Abstract

Abstract Solar-driven water evaporation represents an environmentally benign method of water purification/desalination. However, the efficiency is limited by increased salt concentration and accumulation. Here, we propose an energy reutilizing strategy based on a bio-mimetic 3D structure. The spontaneously formed water film, with thickness inhomogeneity and temperature gradient, fully utilizes the input energy through Marangoni effect and results in localized salt crystallization. Solar-driven water evaporation rate of 2.63 kg m −2 h −1 , with energy efficiency of >96% under one sun illumination and under high salinity (25 wt% NaCl), and water collecting rate of 1.72 kg m −2 h −1 are achieved in purifying natural seawater in a closed system. The crystalized salt freely stands on the 3D evaporator and can be easily removed. Additionally, energy efficiency and water evaporation are not influenced by salt accumulation thanks to an expanded water film inside the salt, indicating the potential for sustainable and practical applications.