MoS2-PVDF/PDMS based flexible hybrid piezo-triboelectric nanogenerator for harvesting mechanical energy

Abstract

A green energy generating device, which can harvest the energy from ambient sources present in our surroundings to fulfill the energy needs of future technologies without polluting our surrounding are becoming more in demand. To extract electrical energy from mechanical vibrations, nanogenerators based on piezoelectric and triboelectric phenomena are being explored recently. When a piezoelectric material is used as one of the two components in the triboelectric nanogenerator, these two effects can be coupled. It is possible to further improve the output efficiency of the nanogenerator by integrating these two effects to form a hybrid nanogenerator. In this work, we have fabricated the different piezoelectric energy harvesters based on MoS2-PVDF materials by varying the weight percentage (0%, 2%, 5% and 7 wt%) of MoS2. The piezoelectric output of the PVDF was found to be increased due to the incorporation of MoS2. In comparison to bare PVDF film, the piezoelectric nanogenerator based on 7 wt% of MoS2 as filler in PVDF shows nearly 2-fold increase in output voltage from 9.4 V to 18.0 V. Further, a piezo-tribo based hybrid nanogenerator (HNG) is fabricated by integrating the MoS2-PVDF film having highest piezoelectric output with PDMS thin film as two layers required for the HNG device. It may be highlighted that the introduction of MoS2 in PVDF matrix not only enhanced the piezoelectric output which may be attributed to the intrinsic piezoelectric nature of MoS2 and enhanced β-phase crystallization, the triboelectric charge generation also gets enhanced. The enhanced hybrid output performance may be attributed to its increased dielectric property and surface roughness. The MoS2-PVDF/PDMS based HNG provides an output voltage of 35.3 V, which is 1.6 times greater than the HNG based on bare PVDF/PDMS layers. The generated output power successfully lit up 21 LED bulbs by the application of a small mechanical force generated by finger tapping and could charge a 10 μF capacitor to ∼9 V in ∼400 s. The present findings suggest that by hybridizing different device mechanism in a single device the energy harvesting performance of resulting HNG can be enhanced, making it possible to drive smart wearable electronic devices.