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.