Water management by hierarchical structures for highly efficient solar water evaporation

Abstract

Solar water evaporation is a sustainable and efficient way to produce freshwater. Seeking highly efficient photothermal materials is an important step to achieve high evaporation rate. However, the effect of water interfacial area is rarely paying attention although a few reports demonstrated high evaporation rate from micro-/nanostructure device. In this work, we introduce a new term-water mass per unit surface area (WMUA) to bridge the water mass and interfacial area. We regulate the WMUA by different commercial porous materials to realize the water management in the device, which further affects the evaporation rate. The optimized device is composed of suede sponge/filtrate paper/polydopamine as water transportation/water reducer/photothermal material, which achieve the evaporation rate of 1.8 kg m-2 h-1 and energy efficiency of ~92%. It opens up a new strategy to rationally design the device structure and promote the evaporation rate and push the field into a new stage.