Enhancing stability of interfacial solar evaporator in high-salinity solutions by managing salt precipitation with Janus-based directional salt transfer structure

The interfacial solar evaporator is promising for efficient clean water production. However, it remains a challenge to achieve stable evaporation in high-salinity solutions and recover salts simultaneously. Here we developed an evaporator with a Janus-based directional salt transfer structure to address this issue by guiding saline solution transport and salts precipitation designedly. An average stable evaporation rate of 1.21 ± 0.07 kg m-2 h-1 with the salt recovery of 876.3 ± 2.4 g m-2 d-1 was achieved in 10 wt% NaCl solution for continuous 5 days under the irradiation intensity of 1 kW m-2. In addition, the Janus-based evaporator could be used to treat simulated high-salinity organic wastewater indoors and seawater outdoors, with an evaporation rate of 1.12 ± 0.06 kg m-2 h-1 and 6.88 ± 1.01 kg m-2 d-1, respectively. The condensed water produced by the evaporator could reach the drinking water standards of WHO. We believe that our work could provide novel guidance to design solar evaporators with zero liquid discharge.