Enhanced Liquid–Solid Triboelectric Nanogenerators with SiO₂@Cu-Doped Composite Coating for Droplet Energy Harvesting

Rainwater is a clean and abundant energy source, and the liquid-solid triboelectric nanogenerator (LS-TENG) has emerged as a promising technology for harvesting and converting raindrop energy into electricity. Despite its potential, practical applications of LS-TENG have been limited by its low output performance and complex fabrication processes. Herein, we propose a simple and efficient strategy for constructing high-performance LS-TENG by introducing a novel composite triboelectric layer composed of poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) (PVDF-HFP) doped with SiO₂@Cu and 1H,1H,2H,2H-perfluorooctyltriethoxysilane. This design simultaneously enhances the dielectric constant and hydrophobicity of the triboelectric coating through a polarization effect and surface tuning. As a result, the LS-TENG achieves an excellent output voltage of 19 V and a current of 6.7 μA from a single waterdrop, corresponding to 2.5 and 2.8 times those of undoped PVDF-HFP, and can successfully power small electronic devices. Furthermore, the entire LS-TENG, including both the triboelectric and electrode layers, is fabricated via facile, in situ coating processes, offering good scalability, substrate adaptability, and optical transparency. Therefore, this work integrates material-level output enhancement with process-level simplicity, holding great potential for practical applications in droplet energy harvesting.