Hierarchical structures hydrogel evaporator and superhydrophilic water collect device for efficient solar steam evaporation

Efficient light absorption and trapping are of vital importance for the solar water evaporation by hydrogel-based photothermal conversion materials. Conventional strategies are focused on the development of the composition and structure of the hydrogel's internal network. In our point of view, the importance of the surface structure of hydrogel has usually been underestimated or ignored. Here inspired by the excellent absorbance and water transportation ability of biological surface structure, the hierarchical structured hydrogel evaporators (HSEs) increased the light absorption, trapping, water transportation and water-air interface, which is the beneficial photothermal conversion and water evaporation. The HSEs showed a rapid evaporation rate of 1.77 kg·m-2·h-1 at about 92% energy efficiency under one sun (1 kW·m-2). Furthermore, the superhydrophilic window device was used in this work to collect the condensed water, which avoids the light-blocking caused by the water mist formed by the small droplets and the problem of the droplets stick on the device dropping back to the bulk water. Integrated with the excellent photothermal conversion hydrogel and superhydrophilic window equipment, this work provides efficient evaporation and desalination of hydrogel-based solar evaporators in practical large-scale applications.