A Flexible Piezoelectric PVDF-TiO₂ Nanofibrous Membrane for Intelligent Photocatalytic Performance

<br/><b>Abstract</b><b>：</b><br/>Piezoelectric materials are extensively used in the application of energy harvesting and sensing devices and they have recently attracted much attention by the scientific community. Among them, piezoelectric polymers have special advantages, such as lightweight, deformability, and flexibility, which make them have the potential to become soft electronics. PVDF has become the most widely investigated piezoelectric polymer material because of its excellent characteristics (like chemical resistance, UV stability, mechanical strength) and acceptable price. Electrospinning can produce nano- or micro-fiber membranes with high surface area; moreover, the mechanical stretching and electric polarization during the process can in situ improve the piezoelectric property of PVDF. Therefore, electrospinning becomes an effective and simple method for preparing a piezoelectric-related PVDF membrane.¹ For most catalysts, the limited catalytic efficiency and difficulty in recovering astrict their development and practical applications. When the catalysts are combined with a matrix, the catalysts are easily recycled and reused, meantime the uniform distribution of catalysts on substate can reduce aggregation and increase the surface area of catalysts. In addition, when a piezoelectric material is applied as the matrix, since the piezoelectric field formed in the piezoelectric material can accelerate the migration of electrons and reduce the recombination between electrons and holes, the catalytic efficiency can be improved.²<br/>The current work aims to show the production, characterization, and photocatalytic performance of nanostructured membranes based on electrospun PVDF matrix and TiO₂ catalysts. PVDF-TiO₂ core-sheath nanofiber membrane is prepared by coaxial electrospinning with PVDF solution and TiO₂ solution as the core and sheath. Two steps are carried out in order to investigate the piezo-catalytic activity of the proposed nanofibrous membranes:<br/>● Evaluation of TiO₂ solutions with different TiO₂ concentrations, solvents, and additions in order to find the proper one for achieving good morphology PVDF-TiO₂ core-sheath nanofibers with a uniform TiO₂ coverage;<br/>● Evaluation of the core-polymer solution: PVDF, P(VDF-TrFE), PAN are used as core solutions in coaxial electrospinning for investigating the performance of core-sheath nanofiber membranes with different piezoelectric properties.<br/>All the obtained membranes are characterized in terms of morphology, piezo-catalytic activity, stability, and potential service life. The obtained results allowed us to consider the proposed approach as a valid solution in the development of new advanced solutions for wastewater treatment.<br/><br/><b>Reference:</b><br/><i>(1) Azzaz, C. M.; Mattoso, L. H. C.; Demarquette, N. R.; Zednik, R. J. Polyvinylidene fluoride nanofibers obtained by electrospinning and blowspinning: Electrospinning enhances the piezoelectric β-phase – myth or reality? Journal of Applied Polymer Science <b>2021</b>, 138, 49959.</i><br/><i>(2) Liang, Z.; Yan, C.-F.; Rtimi, S.; Bandara, J. Piezoelectric materials for catalytic/photocatalytic removal of pollutants: Recent advances and outlook. Applied Catalysis B: Environmental <b>2019</b>, 241, 256-269.</i>