A Study of Contact Electrification Process on PVDF-Metal Interface: Effect of β Phase Composition

Abstract

Recently, triboelectric nanogenerators (TENGs) are getting considerable attention as an energy harvesting tool that can convert random mechanical energy into electricity due to the wide material selection, low cost, and easy fabrication. TENGs work by contact electrification on the interface and electrostatic induction on the electrodes when two surfaces contact and separate. Herein, the study of the contact electrification process on the metal-polyvinylidene difluoride (PVDF) interface is conducted focusing on the effect of beta phase content on the electrical properties of the PVDF films. It is found through the EFM and KPFM surface electrical studies that a higher beta phase promotes stronger electrostatic interactions and enhances electron-cloud overlap with the metal coated cantilever tip that leads to higher amount of charge transfer. Additionally, there is overall enhancement of the TENGs electric output performance for a higher beta phase containing PVDF films and the maximum electric output of 8.1 V and 12.2 nA is obtained for the TENG made with 79% beta phase PVDF film. Polyvinylidene fluoride (PVDF) is polymorphic polymer commonly used in piezoelectric and triboelectric nanogenerator applications. A higher polar beta phase content in PVDF films is found to increase electrostatic attraction between the polymer and metal, leading to enhanced charge transfer observed through kelvin probe force microscopy potential measurements as well as electrical output performance of triboelectric nanogenerators.image