Morphology-driven multifunctionality: tailoring ZnO for enhanced EMI shielding and energy harvesting in PVDF/MWCNT nanocomposites

Abstract

This research establishes a critical correlation between the morphologies of zinc oxide (ZnO) inclusions and the emergent electrical, electromagnetic interference (EMI) shielding, and energy harvesting (piezoelectric and triboelectric) properties of poly(vinylidene fluoride) (PVDF)–multiwalled carbon nanotube (MWCNT) hybrid nanocomposites. Strikingly, incorporation of a low concentration (0.05 wt%) of ZnO nanospheres, with polyvinylpyrrolidone (PVP), led to a two-order-of-magnitude enhancement in the electrical conductivity of the PVDF–7 wt% MWCNT matrix, surpassing the binary composite and a four-order-of-magnitude increase over the ZnO rod-modified counterpart. This morphological advantage was translated into superior EMI shielding, with the ZnO nanosphere-incorporated hybrid nanocomposite (0.2 mm thickness) exhibiting a total shielding effectiveness of 24.72 dB, nearly double that of the rod-modified system (12.91 dB) at 10 GHz. Conversely, the hybrid nanocomposite with ZnO rods resulted in a higher piezoelectric output voltage of 3.95 V under mechanical stimulus, while ZnO nanosphere inclusion resulted in a higher triboelectric output voltage of 6.72 V. These divergent behaviours are mechanistically linked to the electroactive γ-phase content of PVDF, confirmed through X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry, and the surface roughness of the composite, respectively. The distinct dispersion characteristics of the ZnO fillers within the PVDF–MWCNT matrix were elucidated through dynamic mechanical analysis.