A simple, mild and versatile method for preparation of photothermal woods toward highly efficient solar steam generation

Wood-based photothermal materials for solar steam generation have drawn great attentions in recent years. Until now, surface coating and surface carbonization have been developed to transform woods into photothermal materials. Although great achievements have been made, there are still some challenges. Firstly, carbonization needs high temperature and will deprive the wood's superhydrophilicity, which is disadvantage for the wood to against fouling of oil spills. Secondly, most black coatings such as carbon black will fall off the substrates due to the limited interaction between coating and substrates. Moreover, it is still difficult for surface carbonization and most surface coatings to turn woods with any shapes blackness, which will limit the structure design toward further improved solar steam generation performance. Herein, a simple, mild and versatile method without high temperature or any noble metals has been developed to transform various woods with any shapes into black materials for solar vaporization of water. The resultant wood exhibits high solar-to-evaporation efficiency (about 90%) under one sun illumination, outstanding stability (good acid-base resistance property, anti-rinsing at 3000r/min for 100 h, withstand cyclic frost-thaw for 100 times, withstand ultrasound treatment for 2 h), and desirable anti-crude oil-fouling performance, which is very attractive for its application in the ocean. Most importantly, structural designs can be easily realized via this method, leading to the significantly improved water evaporation rate from 1.34 kg m−2 h−1 to a record high rate of 1.85 kg m−2 h−1 for wood-based photothermal materials under one sun. This study represents a new avenue for fabrication and design of wood-based photothermal materials, and will contribute to the global effort in addressing world water and energy issues.