Hierarchically structured bilayer Aerogel-based Salt-resistant solar interfacial evaporator for highly efficient seawater desalination

Solar vapor generation (SVG) has emerged as a promising technique of harvesting solar energy for producing fresh water from seawater. However, two main problems of insufficient energy utilization and salt accumulation on evaporation surfaces are still challenging issues for the broad application of this technique. In this work, we demonstrate a hierarchically structured bilayer aerogel by in situ deposition of polypyrrole (PPy) inside the top layer of cellulose. The light-absorbing PPy/cellulose composite with three-dimensional (3D) hierarchical structures served to convert solar energy into thermal energy and localize the heat to power the vaporization of water contained in the cellulose network. While the porous and hydrophilic cellulose matrix enabled continuous water transport and replenishment to the upper evaporative layer. Moreover, several microcracks were formed at the PPy/cellulose surface, which assisted vapor escape and salt re-dissolution. As a result, the prepared PPy/cellulose aerogel enabled a high seawater evaporation rate of 1.42 kg m- 2 h-1 at energy efficiency of 97.8% under one sun illumination. The SVG system also exhibited highly efficient and stable evaporation performance in seawater without surface salt accumulation over one week.