Flexible Electrospun PVDF Piezoelectric Nanogenerators with Electrospray-Deposited Graphene Electrodes

Today, there is a great demand for the development of portable, lightweight, flexible, and stable devices that produce and store energy to provide the power that wearable electronics and smart textile materials need. For this purpose, in recent years, researchers have focused on the development of nanofiber-based nanogenerators that have high surface areas thanks to their nanofibrous structures. Therefore, this study presents the development of piezoelectric nanogenerators made of poly(vinylidene fluoride) (PVDF) nanofibers and graphene-based flexible electrodes via electrospray deposition (ESD) technique using electrospinning devices. First, graphene oxide (GO) was electrosprayed onto the PVDF-nanofiber surface, then, the coated GO layer was reduced by chemical treatment to obtain reduced-GO (rGO) and to increase the electrical conductivity. With the ESD technique, it has been observed that graphene oxide nanosheets successfully wrapped on the nanofibers without agglomerating, and this effect was further enhanced by the reduction process. The effect of different thicknesses of graphene electrodes on the efficiency of nanogenerators was investigated. As a result, a maximum peak-to-peak voltage of 1.00 V was produced by a rGO-sprayed nanofiber-based nanogenerator, while 0.688 V was obtained with pure PVDF nanofibers. Also, "voltage-per-gram" analysis showed that the output voltage was directly related to the electrode morphology and thickness. Graphical Abstract