Capillary-flow-optimized Heat Localization Induced by Air-enclosed 3D Hierarchical Network for Elevated Solar Evaporation.

Solar evaporation is a cost-effective way for obtaining clean water using renewable energy. However, many solar evaporation devices still show unsatisfactory performance and suffer from inefficient utilization of absorbed solar energy. Herein, numerical simulations of solar evaporation demonstrate that the heat management is a key factor governing the solar evaporation efficiency. This prediction is confirmed through using a bilayered solar steam generation architecture (HS-CB) both in lab- and pilot-scale study. The HS-CB consists of carbon black (CB) film as a solar-thermal conversion layer and a 3D hierarchical polyvinylidene fluoride (PVDF) skeleton crosslinking hollow glass microspheres (HSs) as a heat localization and water-transporting layer. A balance between thermal insulation and capillary-driven water transport can be reached by tuning the porosity of the thermal-insulating layer, thus inducing optimized heat localization. The proposed structure evaporates water with an efficiency of 82.1% under one sun irradiance (1 kW m-2) in lab and can even stably produce 4.63 L m-2 d-1 (average efficiency of 37%) of purified water from highly concentrated industrial waste water in pilot study, demonstrating its promising potential for application in seawater desalination and brackish water purification.