Efficient-heat-utilization 3D T-shaped porous sponge assists 2D photothermal films to achieve self-acting salt rejection and extra evaporation under high-concentration brine

Abstract

Solar-driven interfacial steam generation (SISG) technology for seawater desalination is a green solution to the current freshwater crisis. However, salt accumulation and heat loss in the SISG system under high-concentration brine still have not been solved simultaneously. Inspired by the 3D evaporation structure design, we proposed a strategy to achieve self-acting salt rejection and extra evaporation. The strategy is based on a 3D T-shaped porous sponge (3DTPS), which helps various 2D photothermal films achieving self-acting salt rejection and extra evaporation simultaneously. 3DTPS provides a large number of water exchange channels for the 2D photothermal film. Therefore, under one sun (1 kW m−2), even if the brine concentration is as high as 20 wt%, salt-free can be maintained. When the hot is transferred downward, the T-shaped structure enables the 3DTPS to expose its heated surface to a greater extent in the air. 3DTPS (D = 2.5 cm) is used as an additional evaporation structure for extra evaporation, resulting in an increase of evaporation efficiency for an extra more than 21%.