A yolk@shell superhydrophobic/superhydrophilic solar evaporator for efficient and stable desalination

Abstract

Solar-driven interfacial evaporation for desalination is a very promising strategy for obtaining clean water while avoiding an energy crisis and environmental pollution. However, the poor evaporation performance and long-term salt-resistance of conventional solar evaporators in seawater seriously hinder their applications for practical solar desalination. Here, we report a yolk@shell superhydrophobic/superhydrophilic solar evaporator for efficient and stable desalination. The evaporator was prepared by coating a superelastic superhydrophobic silicone sponge with multi-walled carbon nanotubes (MWCNTs) on the top surface followed by changing the external surface to be superhydrophilic. The silicone/MWCNT evaporator features high sunlight absorption and photothermal conversion by the silicone/MWCNT hybrid layer, sufficient water supply and rapid salt dissolution in the superhydrophilic shell, and low heat loss enabled by the superhydrophobic yolk. Consequently, the evaporator shows a stable evaporation rate of 1.72 kg m⁻² h⁻¹ during a 200 h continuous solar desalination of seawater under 1 sun. Furthermore, 11.8 kg m⁻² of clean water could be collected in a sealed setup using the evaporator upon 10 h continuous solar desalination. The high-performance evaporator may find practical applications for solar desalination of seawater and wastewater, as it can be prepared by a very simple procedure.