Bioinspired Fractal Design of Waste Biomass‐Derived Solar–Thermal Materials for Highly Efficient Solar Evaporation

Abstract Solar evaporation is considered a promising technology to address the issue of fresh water scarcity. Although many efforts have been directed towards increasing the solar–thermal conversion efficiency, there remain challenges to develop efficient and cost‐effective solar–thermal materials from readily available raw materials. Furthermore, further structural modification of the original biomass structure, particularly at multiple length scales, are seldom reported, which may further improve the solar–thermal performance of these material systems. Herein, a novel low‐cost system is developed based on a common bio‐waste, pomelo peels (PPs), through a bioinspired fractal structural design strategy, fractal carbonized pomelo peels (FCPP). This FCPP system shows an extremely high solar spectrum absorption of ≈98%, and marvelous evaporation rate of 1.95 kg m −2 h −1 with a solar–thermal efficiency of 92.4%. In addition, the mechanisms of the evaporation enhancement by fractal structural design are identified by numerical and experimental methods. Moreover, using FCPP in solar desalination shows great superiority in terms of cost and its potential in sewage treatment is also studied. The present work is an insightful attempt on providing a novel proposal to develop bio‐waste‐derived solar–thermal materials and construct biomimetic structures for efficient solar evaporation and applications.