Highly Sustainable Hybrid Liquid Epoxidized Natural Rubber Hydrogel for Enhanced Freestanding Triboelectric Nanogenerator Applications

Abstract

Efficient material development for triboelectric nanogenerators (TENGs) is crucial for sustainable energy. This study improves the performance of a TENG with a flexible biocomposite hydrogel made of liquid epoxidized natural rubber (LENR) and reduced graphene oxide (rGO). By integrating poly(acrylamide-co-acrylic acid) (P(Aam-co-AA)) and copper sulfate (CuSO4), a hydrophilic hydrogel with improved mechanical and electrical properties was developed. Characterization by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and differential scanning calorimetry (DSC) showed significant improvements in mechanical strength and triboelectric performance. In particular, the hydrogel with 0.1% rGO achieved the highest conductivity of 6.6647 x 10−3 S/m, the lowest resistivity (150.4529 Ω-m) and a capacitance of 23 mF, which supplied up to 3V to an LED, while maintaining a glass transition temperature (Tg) of about -8°C. Its dual network structure, combining ionic cross-linking and a flexible polymer backbone, supports robust performance under strain and offers a promising approach to sustainable energy harvesting.

Keywords: hybrid hydrogel, triboelectric nanogenerators, standing electrode mode, TENGs