Churros-like Polyvinylidene Fluoride Nanofibers for Enhancing Output Performance of Triboelectric Nanogenerators.

Triboelectric nanogenerators (TENGs) have emerged as a next-generation sustainable power source for Internet of Things technology. Polyvinylidene fluoride (PVDF) nanofibers (NFs) have been investigated widely to enhance the TENG performance by controlling their polarity; however, controlling the surface morphology of the PVDF NFs has rarely been studied. Here, surface-roughened, churros-like PVDF NFs were fabricated by controlling the solvent evaporation kinetics. The solvent evaporation rate was modulated by varying the relative humidity (RH) during the electrospinning process. With increasing RH, the fraction of polar β-phase in the PVDF NFs increased, the specific surface area of the PVDF NFs increased gradually and the surface morphology changed from smooth to rough, finally resulting in a churros-like structure. Therefore, the output performance of the TENG devices was enhanced with increasing RH, because of the combined effects of the enlarged surface area and the increased fraction of the polar phase in the PVDF NFs. The TENG device with the churros-like PVDF NFs showed an output voltage of 234 V, current of 11 μA, and power density up to 1738 μW/cm, giving it the capability to turn on 60 series-connected commercial light-emitting diodes without using an external charge storage circuit.