Petal-Inspired Superhydrophobic Paper from Lignin-Cellulose for Sustainable Raindrop Energy Harvesting

Raindrop kinetic energy represents a sustainable and distributed energy source. However, conventional materials for harvesting rain energy often depend on petroleum-based and fluorinated compounds, which raise environmental concerns and suffer from interfacial instability. This study proposes a fluorine-free, petal-inspired superhydrophobic interface fabricated from cellulose paper and esterified modified lignin. By incorporating long-chain alkyl groups to enhance lignin’s the hydrophobicity, and constructing multiscale rough structures on the paper surface, the interfacial drainage behavior and charge conversion capability are synergistically improved. The resulting paper-based superhydrophobic interface exhibits excellent water repellency (contact angle of 163°), mechanical durability, and self-cleaning properties, effectively resisting droplet retention and particle adhesion under diverse environmental conditions. The developed raindrop-driven triboelectric nanogenerators (R-TENGs) achieves an output voltage of 4.7 V and a current of 470.1 nA under raindrop impact, successfully powering an LED device. This material shows potential for application in rooftop or outdoor environments, where it can sustainably harvest raindrop energy to supply power for low-consumption electronics. Furthermore, this work provides a fluorine-free strategy that integrates the functionalization of natural materials with biomimetic structural design, offering a sustainable and environmentally friendly route for efficient raindrop energy harvesting and the development of next-generation paper-based flexible electronics.