Blackbody-Inspired Array Structural Polypyrrole-Sunflower Disc with Extremely High Light Absorption for Efficient Photothermal Evaporation.

The three-dimensional (3D) structural design of solar evaporators has been considered as one of the most promising approaches toward enhancing photothermal performance by improving light absorption and the available evaporation area. Herein, polypyrrole-decorated 3D array structural sunflower discs (PPy-SFD) were prepared for solar steam generation, thereby turning SFD biomass waste into valuable materials. The SFD can absorb a majority of the incident light because of numerous light reflections from each natural 3D array structural unit, and therefore behaves similar to a blackbody. Moreover, a facile pyrrole polymerization method was introduced to further improve SFD light absorption and enhance the photothermal performance of SFD. This circumvents expensive consumption fabrication processes. The black PPy-decorated SFD shows a light absorption of 99.3% across the entire solar spectrum coupled with mechanical stability. During photothermal evaporation, the increased evaporation area of the 3D array structural SFD could effectively reduce heat loss to the environment because the inherent microporous structure of the SFD leaves and cellulose hydrophilicity provide channels for water transport. The PPy-SFD-based evaporator could reach an evaporation rate of 1.74 kg m h under 1 sun. Thus, the 3D array structural PPy-SFD is a possible candidate for high-efficiency photothermal evaporators.