Tailoring polypyrrole-based Janus aerogel for efficient and stable solar steam generation

Seeking an efficient and robust evaporator is the central goal of solar-driven interfacial steam generation. Here, a free-standing Janus aerogel with rough hydrophobic upper layer and smooth hydrophilic bottom layer was tailored by freeze drying of polypyrrole-polyvinyl alcohol (PPy/PVA) colloidal solution, followed by acetalization treatment and selective fluorination decoration. PPy/PVA-F Janus aerogel has a structure integrated in the form of different microscopic layers and chemical compositions, endowing it with omnidirectional light absorption , stable floating on water, enhanced evaporation performance, and salt rejection capability. Due to the reduced vaporization enthalpy, evaporation rate of 1.68 kg·m −2 ·h −1 with solar-to-vapor efficiency of 94.7% was obtained under 1-sun irradiation using the Janus aerogel. Furthermore, the Janus aerogel demonstrated good recyclability and long-term durability at different radiation intensities . This Janus aerogel had satisfactory availability for solar desalination and sewage treatment . The strategy to integrate different microscopic layers and chemical compositions in a Janus aerogel holds great promise for the design and application of Janus evaporators in the field of solar steam generation.