Tailoring of Polypyrrole Wrapped Cotton Fiber Sponge for Simultaneous Solar Steam and Solar Thermoelectric Generation

Solar steam generation (SSG) using floatable evaporators to absorb solar energy and generate heat at the water–air interface has attracted increasing interest in achieving water purification and desalination. Using biodegradable and porous biomass materials as evaporators to fabricate high-performance SSG devices is a promising route, but the poor efficiency and fussy and energy-intensive manufacturing process for biomass material-based evaporators will restrict their practical application. Here, an old commercial cotton quilt is used to prepare porous cotton fiber sponges (CFS) via a simple and scalable mechanical foaming strategy. After being decorated by the polypyrrole (PPy), the CFS@PPy sponge with a hierarchical porous structure shows broadband light absorption capacity, good hydrophilicity, and excellent photothermal capacity. The obtained sponge can be directly used as an evaporator floating on the seawater and shows a high steam-generation efficiency of 85.07% under 1 sun irradiation. Additionally, it can be used as a photothermal material to construct a solar thermoelectric generation (STG) device and achieve an enhanced open-circuit voltage (V out ) of 0.4 V and output current (I out ) of ≈59.6 mA under 5 sun irradiations. With the help of a boost converter, the power generation from the STG device can continuously charge the electric bulb and wristband.