Role of rGO on mechanical, thermal, and piezoelectric behaviour of PVDF-BTO nanocomposites for energy harvesting applications

The low-cost and highly flexible piezoelectric nanogenerators (PENGs) have potential applications in mechanical energy harvesting and low power electronics. The low piezo response of PVDF limits its use in commercial sensory applications. In this work, a Polyvinylidene fluoride (PVDF) is reinforced with fixed quantity of Barium titanate (BTO) and varying concentrations of reduced graphene oxide (rGO) to enhance piezoelectric behaviour of PVDF films. Effect of higher rGO reinforcement (over 0.45 wt%) on PVDF-BTO composite energy harvesting performance was studied for the first time using solvent casting approach followed by electrode poling process. Structural properties along with average crystalline size and lattice strain of PVDF-BTO-rGO nanocomposites were calculated using XRD technique with Williamson-Hall approach. Increment in electroactive beta phase from 54 to 73% has been observed by loading rGO in PVDF-BTO nanocomposites. For the first time, optimal rGO content in PVDF-BTO nanocomposites to achieve maximum mechanical properties is studied. Young's modulus, tensile strength, breaking strain, storage modulus, viscosity, and hardness of PVDF-BTO-rGO films showed remarkable increment compared to PVDF-BTO nanocomposites respectively. The PENG devices were subjected to continuous finger tapping, film twisting and thumb pressing using human hand to record piezoelectric output for poled and unpoled samples. The PENG devices displayed significant enhancement in piezoelectric output voltage from 0.98 V for pure PVDF to 4.1 V for PVDF-BTO-rGO when rGO content is 1.25 wt% for finger tapping condition.