Highly Salt-Resistant interfacial solar evaporators based on Melamine@Silicone nanoparticles for stable Long-Term desalination and water harvesting

Interfacial solar-driven evaporation (ISE) is one of the most promising solutions for collecting fresh water, however, poor salt-resistance severely limits the long-term stability of solar evaporators. Here, highly saltresistant solar evaporators for stable long-term desalination and water harvesting were fabricated by depositing silicone nanoparticles onto melamine sponge, and then modifying the hybrid sponge sequentially with polypyrrole and Au nanoparticles. The solar evaporators have a superhydrophilic hull for water transport and solar desalination, and a superhydrophobic nucleus for reducing heat loss. Spontaneous rapid salt exchange and reduction in salt concentration gradient were achieved due to ultrafast water transport and replenishment in the superhydrophilic hull with a hierachical micro-/nanostructure, which effectively prevents salt deposition during ISE. Consequently, the solar evaporators have long-term stable evaporation performance of 1.65 kg m-2h-1 for 3.5 wt% NaCl solution under 1 sun illumination. Moreover, 12.87 kg m- 2 fresh water was collected during consecutive 10 h ISE of 20 wt% brine under 1 sun without any salt precipitation. We believe that this strategy will shed a new light on the design of long-term stable solar evaporators for fresh water harvesting.

Automated summary

Silicone nanoparticles were deposited onto melamine sponge and modified with polypyrrole and Au nanoparticles to fabricate highly saltresistant solar evaporators for stable long-term desalination and water harvesting. These solar evaporators have a superhydrophilic hull for water transport and solar desalination, and a superhydrophobic nucleus for reducing heat loss. They achieved spontaneous rapid salt exchange and reduction in salt concentration gradient due to ultrafast water transport and replenishment in the superhydrophilic hull with a hierachical micro-/nanostructure, effectively preventing salt deposition during interfacial solar-driven evaporation (ISE). These solar evaporators demonstrated long-term stable evaporation performance and the ability to collect fresh water without any salt precipitation.