A solar evaporator based on hollow polydopamine nanotubes with all-in-one synergic design for highly-efficient water purification

Abstract

Capturing sunlight directly and converting it to heat energy to facilitate water evaporation offers an opportunity to produce freshwater in an energy saving and environmentally benign manner. Solar vapor generation (SVG) is a complex process, which could be divided into four major sub-processes, i.e. photothermal transformation, thermal transmission, water transportation and water evaporation. Therefore, the biggest challenge to achieve high efficient SVG is the synergic integration of these sub-processes. Herein, an all-in-one synergic strategy for SVG considering all the above sub-processes has been developed using polydopamine nanotubes (PDA-t) as the basic unit. Owing to the intrinsic nature and hollow nanotube morphology, PDA-t can simultaneously and synergistically promote all the sub-processes of SVG, resulting in high SVG rates up to 2.5–3.6 kg m⁻² h⁻¹ with different exposure heights above water under 1 sun. Furthermore, floating PDA-t based evaporators have good long-term durability and excellent water purification performance for brine and sewage.