Sustainable self-cleaning evaporator for long-term solar desalination using gradient structure tailored hydrogel

Interfacial solar evaporation has been demonstrated as a promising strategy to mitigate water scarcity. However, for practical application in marine environment, the accumulation of salt and growth of microorganisms such as bacteria will cause scarring and fouling of the evaporators, depressing the potential for long-term sustainable use. Here, we report a hydrogel evaporator (chitosan/PAAm/PPy) with integrated three-layer structure containing individual functions for heat localization to improve solar evaporation efficiency, salt redissolution and antibacterial growth for sustainable long-term use, as well as management of thermal energy loss, respectively. The as-fabricated hydrogel evaporator presented a high-water evaporation rate of 2.41 kg m-2h−1 under 1-sun illumination, and excellent self-cleaning property against the salt accumulation and bacteria growth. During a two-week continuous evaporation experiment in simulated marine water with 3.5 wt% salinity and mixture of bacteria, the evaporator generated vapor stably in a range of 2.30 ~ 2.41 kg m-2h−1, without noticeable performance decay. Additionally, the hydrogel evaporator shows a stable vapor generation rate during cycled dehydration-hydration processes, as well as against repeated weight loading–unloading tests, indicating its convenience for long-term use and storage.