A simple and controllable black hydrogel coating strategy to prepare self-cleaning and durable evaporator for efficient solar steam generation

The scarcity of water resources has led to an urgent need to utilize seawater to obtain fresh water. Hydrogel evaporator shows great promise for solar seawater desalination . However, hydrogel evaporator faces great challenges in practical application owing to its poor stability and complex preparation. To solve this problem, we reported a simple, controllable and eco-friendly solvent evaporation regulating strategy for the preparation of durable black hydrogel evaporator (Fe-PTPU) for the first time. The strategy can regulate and control the distribution and thickness of the hydrogel coating generated in situ on the evaporator skeleton, which can effectively avoid blocking the evaporator pores, enabling the formation of three-dimensional evaporation and improving the rate of solar steam generation. Additionally, this strategy for preparation of high-strength polyvinyl alcohol hydrogel can avoid repeated freeze-thawing, which is time and energy-saving. The Fe-PTPU showed remarkable evaporation rate as high as 2.65 kg m −2  h −1 and outstanding evaporation efficiency of 90.17 % under one sun. Particularly, it was found that the Fe-PTPU exhibited great stability, flexibility and scalability. Moreover, excellent anti-oil, salt-rejecting and self-cleaning performances of Fe-PTPU were proved. Hence, these properties of Fe-PTPU ensured its high durability and applicability for solar seawater desalination.