Janus Evaporators with Self-Recovering Hydrophobicity for Salt-Rejecting Interfacial Solar Desalination

Abstract

The recent advancements in interfacial evaporation of salty water using renewable solar energy provide one of the promising pathways to solve worldwide water scarcity. Pursuing a stable evaporation rate of water has been the central focus of this field, as it is directly related to the throughput, while salt deposition on the evaporator becomes a critical issue. Although Janus-structured evaporators with an upper hydrophobic layer and a bottom hydrophilic layer have been demonstrated as an effective way to suppress the salt precipitation, the hydrophobic upper layer, achieved usually by some special organic groups, suffers from a photochemical oxidation when exposed to oxidative chemicals in water and high-energy light, resulting in a deteriorated surface hydrophobicity. Here, we report our design of an efficient salt-rejecting Janus evaporator by taking advantage of the self-recovering surface hydrophobicity of poly(dimethylsiloxane) (PDMS) against photochemical damages, which ensures a long-term surface hydrophobicity. With its upper layer partially covered with PDMS, the Janus evaporator demonstrates an excellent salt rejection capability and exhibits a stable evaporation rate of 1.38 kg·m –2 ·h –1 under 1 sun illumination for 400 min of continuous operation, or 90 d of intermittent work. By combining the advantages of high structural integration, long-term salt-rejection, and efficient evaporation, our Janus evaporator holds great promise for the stable production of clean water from seawater.