Ferroelectric nano-heterojunctions for piezoelectricity-enhanced photocatalysis

Abstract

Nanoscale heterojunctions of high dielectric constant piezoelectrics and optoelectronic semiconductors are attractive for photocatalytic degradation of hazardous organic compounds. In this work, such a nano-heterojunction was prepared by mixing of surface-carboxylated ferroelectric BaTiO3 nanoparticles (BTO NPs) and protonated graphitic carbon nitride (g-C3N4). Due to strong electrostatic interactions, intimate contact between BTO NPs and g-C3N4 was achieved for efficient charge separation and transfer. Two piezoelectric BTO NPs were used to prepare the BaTiO3/g-C3N4 heterojunctions: as-received BTO (arBTO) and 950 °C-annealed BTO (anBTO) with larger ferroelectric domains. Under ultrasonication, the photocatalytic degradation rate of levofloxacin by anBTO/g-C3N4 heterojunctions were 0.0462 min−1, which were 9.2 times of arBTO and 3.6 times of those in the absence of ultrasonication. The underlying mechanism was attributed to the higher current density, the accelerated charge separation of photo-activated excitons, and the reduced charge recombination via a synergistic effect of heterostructures and the local piezo-potential generated by the ferroelectric BTO NPs. By combination of thermal annealing of arBTO to enlarge the ferroelectric domains and construction of heterostructures, a highly efficient photocatalyst could be obtained. This study provides us a simple yet effective method to achieve highly efficient photocatalysts using the piezoelectric effect of ferroelectric BTO NPs.