Design of a Separated Solar Interfacial Evaporation System for Simultaneous Water and Salt Collection.

Solar-driven interfacial evaporation (SIE) is very promising to alleviate the freshwater scarcity issue. However, salt deposition on the sample surface will reduce evaporation performance, and compromised light absorption will result in a low water collection rate in conventional SIE apparatuses. Here, we report the design of a separated SIE system composed of a polypyrrole@Co3O4@aluminum sheet and a T-shaped superhydrophilic polyethylene/polypropylene nonwoven fabric right under the sheet. The photothermal surface exposed outside the closed SIE system is separated from the evaporation surface. Thus, salt fouling of solar evaporators is thoroughly avoided and the freshwater collection rate is greatly enhanced. Compared with conventional SIE systems, the separated SIE system has many advantages: simultaneous water and salt collection, a long-term stable evaporation rate even for concentrated brine (1.25 kg m-2 h-1 under 1 kW m-2 (1 sun) illumination, 15 wt % NaCl(aq), ≥120 h), high salt collection efficiency (≥97%), and a high water collection rate under natural sunlight, e.g., 0.72 kg m-2 h-1 in early spring (0.5-0.6 sun, 19-24 °C) and 0.33 kg m-2 h-1 in cold winter (0.3-0.4 sun, -6 to 4 °C). We foresee that the separated SIE system holds great potential for practical freshwater and salt collection from seawater.