Ultrasound and water flow driven piezophototronic effect in self-polarized flexible α-Fe2O3 containing PVDF nanofibers film for enhanced catalytic oxidation

A new piezophotocatalytically active membrane based on polyvinylidene fluoride (PVDF) nanofibers with α-Fe2O3 nanoparticles incorporated into them has been synthesized by electrospinning. The composition, morphology and structure of α-Fe2O3 containing PVDF nanofibers mats were investigated by SEM, XRD, Raman, FTIR, XPS and DSC. Studies have shown that the inclusion of α-Fe2O3 nanoparticles promotes additional crystallization and self-polarization of PVDF into an electroactive β-phase. With the help of XPS, the mechanism of interfacial ion-dipole electrostatic interaction, leading to self-polishing and crystallization of the structure, is shown. Using measurements of VB XPS, UPS and the frequency dependence of the dielectric constant, the role of polarization effects on the formation of long-lived metastable energy states in the electronic structure of PVDF near the Fermi level is shown. Piezocatalytic and piezophotocatalytic activity was assessed by the decomposition of Methylene Blue (MB) under the influence of ultrasound and UV-Vis radiation. The efficiency of piezocatalysis and piezophotocatalysis was 60.4% and 99.5%, respectively. With the help of experiments on the capture of active redox forms, it was found that ∙OH radicals are the main component of the MB degradation. Two different mechanisms of generating ∙OH radicals for piezocatalysis and piezophotocatalysis have been reasonably proposed. The stability of the catalyst was shown after five successive cycles of piezophotocatalysis.