Dual fillers ZrO2/BaTiO3 incorporated PVDF-HFP nanofiber composite for enhanced piezoelectric energy harvesting and piezo catalytic reduction of hexavalent chromium

A novel Piezoelectric Nanogenerator (PENG) was designed and fabricated using electrospun nanocomposite fibers of Poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) with Barium Titanate (BaTiO3) and Zirconium Oxide (ZrO2) as dual fillers. ZrO2 fillers were incorporated at varying loadings into the PVDF-HFP polymer matrix to produce the PBZ nanocomposite fibers. The synergistic effect of BaTiO3 and ZrO2 significantly enhanced the piezoelectric performance of the resulting PBZ composite. The dual fillers also induced the nucleation of the beta-phase in the nanofiber composite, which further improved its piezoelectric properties. This enhancement rendered the composite highly effective for dual applications: energy harvesting and the piezocatalytic reduction of hexavalent chromium (Cr(VI)). The PENG exhibited an open-circuit voltage of 6.3 V, a current of 0.67 mu A, and a power density of 30.91 mW/m2. The device was also tested in real-world scenarios, such as finger tapping and shoe sole applications, additionally it successfully powered up to five LEDs and charged a 1-2.2 mu F capacitor to approximately 1-3 V under an external load of 1 N at 2 Hz. In addition to energy harvesting, the PBZ nanofibers demonstrated remarkable piezocatalytic activity by converting highly toxic Cr(VI) to Cr(III), which is biologically essential in trace amounts. The PBZ nanofiber mats achieved an impressive Cr(VI) reduction rate of up to 90.1 % under acidic conditions within 20 minutes and were recyclable for up to five cycles without loss of efficiency. Furthermore, Density Functional Theory (DFT) calculations, focusing on the Density of States (DOS), were performed to elucidate the underlying mechanisms contributing to the observed improvements in piezoelectric and piezocatalytic performance.