Fabrication of amino and fluorine functionalized graphene-based polymer composites to enhance the electromechanical conversion efficiency of TENGs for energy-harvesting applications

The two main factors hindering the practical utilization of triboelectric nanogenerators (TENGs) are low power density and high internal impedance. To address this issue, TENGs with high electromechanical conversion efficiency must be developed. Several techniques have been investigated to improve the TENGs output performance, including surface modifications (physical or chemical) and embedded charge-trap nanomaterials (dielectric or conductive). Herein, we introduce the novel amino-functionalized reduced graphene oxide (AFGO) and graphite-fluorinated polymer (FG) pillars to enhance the tribo-positivity and tribo-negativity of polyurethane (PU) and Ecoflex (EC), respectively. The surface positive-potential of PU is increased almost 2.2 times (from 201 V to 480 V) and negative-potential of Ecoflex is increased 2.1 times (from −848 V to −1813 V) with incorporating AFGO and FG pillars. Functionalized graphene and graphite-based pillars synergistically enhance surface charges (owing to the presence of –NH2 and -F terminating groups) and minimize triboelectric loss (owing to their conductive nature). The effects of the AFGO and FG contents on the electrical performance were studied systematically. The optimized PUAFGO2/EC15FG-TENG exhibited the maximum electrical output performance with an open-circuit potential of 434 V, a short-circuit current of 11. 2 µA, a power density of 1.18 Wm−2 at a load of 40 MΩ, and a charge density of 17.5 µCm−2. The PUAFGO2/EC15FG-TENG showed a mechanical conversion efficiency of 95% and successfully operated 33 LEDs and a stopwatch. Owing to this effectivity, even under low pressures, with a high sensitivity of 9.5 VPa−1 and high mechanical stability, the proposed TENG device could be used as a biomechanical energy harvester in the near future.