In situ polymerization of pyrrole on elastic wood for high efficiency seawater desalination and oily water purification

Solar desalination emerged as a promising and sustainable method for addressing the water shortage issue. Although wood can be converted to photothermal materials by surface coating and carbonization, many challenges such as the poor hydrophilicity, vulnerability to oil contamination and lipophilic micro-organisms of photothermal wood-based materials still remain. Moreover, it is difficult to form a stable chemical bond between the photothermal coating and the wood substrate, which hinders the improvement of corresponding solar evaporator. Therefore, we have prepared a wood-based solar desalination device (PPy-E-Wood) by in situ polymerization of pyrrole monomer on the pre-treated elastic wood. Successfully, efficient steam generation is achieved through the synergistic effect of the high photothermal conversion layer of PPy NPs, and the wood substrate with low thermal conductivity, micro/nano-pores and channels. The hydrophilicity and porous structure of PPy-E-Wood ensure a continuous water supply to its air–water interface, which give it a high solar conversion efficiency of 86% and an evaporation rate of 1.35 kg·m−2·h−1 under 1 kW·m−2. In addition, PPy-E-Wood has excellent structural stability, recoverability, electrical conductivity, and high salinity tolerance. Notably, the salt crystallized on its surface under ultra-high light (3 kW·m−2) can be dissolved by the natural alternation of day and night. Significantly, this wood-based photothermal material could easily realize its structural design and significantly improve its evaporation rate to 1.55 kg·m−2·h−1 or even 1.65 kg·m−2·h−1. Besides, PPy-E-Wood possesses not only the excellent superhydrophilicity and underwater superoleophobicity, but also an outstanding separation efficiency towards oil-in-water emulsions (~ 98%). We hope this work offer a new path to manufacturing and designing the wood-based photothermal materials for alleviating the global water and energy shortage. In this study, an elastic and shape-diversified photothermal matrix material with abundant internal cellulose network was prepared by removing part of lignin from raw wood, which acted as substrate and could be designed with various structures, and loading PPy on its top by in-situ polymerization of pyrrole for achieving photothermal conversion. Under the synergistic effect of superwetting substrate and photothermal top-coating, PPy-E-Wood realize the functions of seawater desalination and oil–water separation, providing a promising solution for water purification.