Enhancing triboelectric performances of electrospun poly(vinylidene fluoride) with graphene oxide sheets

Poly(vinylidene fluoride) (PVDF) is an easy processable and electroactive polymer, widely investigated for the preparation of electrospun membranes for triboelectric nanogenerators (TENG). The presence of graphene oxide (GO) fillers into the PVDF nanofibers, used as electroactive membranes in TENGs, has been reported to improve their performances as GO can act as charge trapping site. Nevertheless, the addition of GO also affects the dielectric and rheological properties of the spinning dispersions and the role of such parameters on the nanofiber morphology has not been clarified yet. In this work, we investigated the effect of GO on the electrospinning process of PVDF–GO dispersions. In particular, we found that the addition of GO in PVDF solutions modifies their rheological properties by increasing their viscosity and enhancing their shear thinning behavior. Consequently, compared to the PVDF solution, the electrospinning process of PVDF–GO composite solutions results in more homogenous and thinner nanofibers. Both PVDF and PVDF–GO nanofibers showed a similar fraction of electroactive PVDF β-phase, which was higher than 80%. This demonstrates that the relative content of β-phase is not the main responsible for the observed improvement in TENG performances. Therefore, besides acting as a charge trapping site, the presence of GO also shrinks the PVDF–GO fibers diameter, resulting in an electrospun membrane with increased specific surface area compared to the PVDF counterpart.