Unlocking the hybrid piezo and pyroelectric nanogenerators performance by SiO2 nanowires confinement in poly(vinylidene fluoride)

We report on the development of a novel flexible piezo/pyro-electric nanogenerator (PPNG) that combines a uniform film of poly(vinylidene fluoride) (PVDF) infiltrated into vertically supported SiO2 nanowires (NWs) to enhance both piezoelectric and pyroelectric energy harvesting capabilities. The synthetic procedure involves a low-temperature, multi-step approach, including the soft-template formation of SiO2 NWs on a flexible substrate, followed by the infiltration of a PVDF thin film (TF). The plasma-enabled fabrication of SiO2 NWs facilitated vertical alignment and precise control over the surface microstructure, density, and thickness of the confined nanostructures. These strategic structural systems promote the development of the most favorable electroactive β- and γ-phases in the PVDF matrix. Notably, electrical poling plays a major role in aligning the random dipoles of the PVDF macromolecular chain in a more ordered fashion to nucleate the amplified electroactive phases. The electrostatic interaction between PVDF and SiO2 NWs, which helps to facilitate the electroactive phase, is confirmed by the surface potential distribution. As a proof-of-concept, the fabricated PPNG exhibited a significant improvement in the instantaneous piezoelectric output power density (P), with a ∼9-fold amplification relative to its bare PVDF TF counterpart. In addition, PPNG has demonstrated excellent stability and durability. Analogously, the pyroelectric coefficient (p) demonstrated a 4-fold superior performance compared to the reference PVDF TF-based PPNG. Thus, the engineered system of SiO2 NWs@PVDF comprising PPNG offers a promising pathway toward multisource energy harvesting capabilities through efficient energy transduction at mechanical excitation frequencies of 10–12 Hz and across a temperature difference of 9–22 K.