2D SnO2 nanosheet/PVDF composite based flexible, self-cleaning piezoelectric energy harvester

Highlights: • 2-D SnO₂ nanosheet/PVDF composite based flexible, self-cleaning nanogenerator. • Remarkable power density (4900 W/m³) and energy conversion efficiency (16.3%). • High output piezoelectric output (45 V) and superior current density (6.25 μA/cm²) • First Gr-IV oxide based inorganic-organic nanogenerator able to power 85 LEDs. • Capable to harvest human motion based and other low frequency mechanical energy. -- Abstract: Flexible piezoelectric nanogenerators have been considered as the most promising candidates in recent years for powering the portable, bendable, and wearable electronics devices by scavenging low frequency biomechanical energy. This work reports an analysis of remarkable output power enhancement of a human-body motion based piezoelectric nanogenerator comprising of self-polarized 2D SnO₂ nanosheet/poly(vinylidene fluoride) (PVDF) nanocomposite. Structural, mechanical, thermal as well as piezoelectric properties of the composites were studied rigorously, which proved that 5 wt% SnO₂ nanosheet/PVDF composite is the most promising one for nanogenerator applications. The inorganic-organic 2D SnO₂ nanosheet/PVDF composite based piezoelectric nanogenerators (PSNG) were found to produce outstanding power output due to the gentle human finger imparting with a maximum voltage of 42 V and current density of 6.25 μA·cm⁻². The output power density of the PSNG reached 4900 W·m⁻³ with an efficiency c.a. 16.3%. The obtained output of the reported nanogenerator is in well agreement with the fundamental piezoelectric theory. The improved performance of the self-polarized composite can be attributed to the incorporation of homogeneously distributed 2D SnO₂ nanosheets (2D SnO₂ NS) having high surface area, which enhances the electroactive β phase contain in PVDF composites as well as piezoelectric properties. The electrical energy (a.c.) generated from the nanogenerator due to gentle human finger imparting was directly utilized to illuminate 85 numbers commercial LEDs and to charge capacitors rapidly through a bridge rectifier. A hydrophobic 2D SnO₂ nanosheet/PVDF composite film (static contact angle of water drop ∼82.6°) was wrapped on the fabricated nanogenerator to attain self-cleaning feature of the PSNG, making the device water and dirt resistive. This work explores a new prospect for self-cleaning Gr-IV oxide/PVDF based high-efficiency, high power density energy harvester scavenging biomechanical energy for realizing next generation flexible self-powered electronics systems.