Drainage-induced arch hydrogel-based interfacial evaporator drives long-term stable solar evaporation

Abstract

Hydrogel has developed into a very important platform in solar interface evaporator. However, the current hydrogel evaporators are usually three-dimensional evaporators, which will consume a lot of raw materials. Thus, a new two-dimensional hydrogel evaporator is urgently needed to alleviate this problem. Here, a double layer hydrogel evaporator was designed by twice vacuum filtration. Furthermore, through the arched design and the introduction of concentrated brine drainage system, the hydrogel evaporator has enhanced water transportation and tailored water transportation path. Such a unique drainage evaporation system greatly improves the stability of the evaporator. Thereby, a good balance is established between photothermal conversion and water supply, and solar energy is utilized efficiently. It can remain stable in continuous evaporation for up to 12 h with an excellent evaporation rate of 2.70 kg m⁻² h⁻¹ under 1 sun irradiation. Meanwhile, the drainage system realized the 1.8 × 10⁻¹⁰ mol m⁻² s⁻¹ diffusion flux of concentrated brine. Through one-time freeze-drying preparation, an arch-shaped drainage evaporator was used to prepare an evaporation area of more than 20 cm². With the self-made condensate collecting device in outdoor environment, the fresh water yield reaches 7.5 L m⁻² d⁻¹. This provides a new scheme for building a new hydrogel evaporator and solving the fresh water crisis.