Synergistically catalytic activities of BiFeO3/TiO2 core-shell nanocomposites for degradation of organic dye molecule through piezophototronic effect

Abstract

The BiFeO3/TiO2 core-shell nanocomposites with the R3C space group is demonstrated to exhibit the superior synergistically catalyst activities, which is a combination of the piezo- and photo-catalytic activities (referred to as the piezophototronic effect). With the application of an ultrasonification and light irradiation, the degradation activity for the decomposition of the dye molecules by the piezoelectric polarization of the BiFeO3/TiO2 core-shell nanocomposites (referred to as the hybrid catalyst, BiFeO3/TiO2 NCs-P) is 432% higher than that of the un-poling BiFeO3/TiO2 nanocomposites (BiFeO3/TiO2 NCs). In responding to the excitation of the mechanical force (ultrasonic vibration), the results demonstrate that the BiFeO3 nanoparticles can effectively reduce the recombination rate of the carriers by the built-in electric field. Subsequently, the redox reaction has taken place on the surface of the hybrid catalyst in the solution to generate the powerful oxidizing radicals and further dissociate the organic dyes. The reaction k constant of the piezophototronic effect is 566% and 388% higher than that of the sole piezocatalytic and the photocatalytic process, respectively. After four consecutive cycling degradation tests, the hybrid catalyst still reaches ~85% of the degradation activity by the piezophototronic effect. Based on the fluorescence luminescence (FL) analysis, the signals associated to the hydroxyl radicals elevate with the increase of the catalysts’ concentration and the ultrasonic vibration time. This work reveals that the hybrid catalysts contains the ferroelectric material, which provides a new catalyst design strategy in the industrial application.