Facile fabrication of functionalized wood evaporator through deep eutectic solvent delignification for efficient solar-driven water purification

Solar-driven sewage purification was considered to be a promising technique for the alleviation of freshwater scarcity issues globally. However, most steam generation devices focused on ultrahigh photothermal conversion and also neglected to develop the potential functions of natural creatures. Here, a deep eutectic solvent (DES) functionalized wood was designed as the supported substrate decorated with black polypyrrole (PPy) to construct low-cost and efficient solar interfacial evaporator. DES modification selectively removed most of the lignin, which enhanced the hydrophilic wetness of wood for the efficient transportation of water from the bottom to the solar interface. The lignin selective removal lowered the thermal conductivity of the evaporator, facilitating the heat location on the gas-liquid interface for efficient steam generation. Most importantly, more cellulose hydroxyl was exposed on the wood surface by the DES process, which was conducive to the in-situ polymerization of pyrrole on the wood surface by hydrogen bond interaction. The prepared PPy-DES wood evaporator achieved a considerable water evaporation rate of about 1.94 kg m- 2 h-1 with a corresponding photothermal conversion efficiency of about 83.4% in one sun, arising from the functionalized design of DES wood and efficient photothermal conversion. For seawater desalination and sewage purification, the prepared evaporator exhibited excellent salt self-cleaning ability and stable wastewater purification performance. It was envisioned that the strategy of functionalized design of natural evaporators would motivate a large-scale application of biomaterials for efficient wastewater purification.