Local dipole enhancement of space-charge piezophototronic catalysts of core-shell polytetrafluoroethylene@TiO2 nanospheres

Abstract

This study demonstrates the hydrothermal treatment of core-shell polytetrafluoroethylene (PTFE) nanoparticles decorated with TiO2 (h-PTFE@TiO2); this material exhibits strain-induced local dipole enhancement of the space-charge piezopotential that improves the photocatalytic effect. Under acoustic cavitation, dielectric barrier discharge and electric dipole formation are initiated in voids within the PTFE nanoparticles and at the TiO2–PTFE interface. The h-PTFE@TiO2 nanoparticles (NPs) have exceptionally high catalytic activity in organic dye degradation because of the local dipole enhancement of photoinduced charge separation with a carrier lifetime of 3.14 ns. The observed rate constant of the h-PTFE@TiO2 NPs in the piezophototronic reaction reaches 0.1388 min−1, which is 17 times that of the photocatalytic reaction (0.0084 min−1) and 66 times that of the piezocatalytic reaction (0.0021 min−1). Computational simulation reveals that large strain-induced space charge piezoelectric polarization induces an internal electric field between the unsaturated PTFE (fluorine vacancies) and TiO2 surface. The piezopotential has a critical role in band bending at PTFE-TiO2 interfaces to enhance the electron-hole separation when PTFE is constrained in TiO2 shells. Results of piezoresponse force microscopy reveal that the piezoelectric coefficient d33 of PTFE is approximately 79.77 pCN−1. The findings provide insights into catalytic activity for environmental remediation.