Linking the enhanced deep NO oxidation of a ferroelectric K0.5Bi0.5TiO3 nanowire photocatalyst to its spontaneous polarization and oxygen vacancies

Abstract

Fast recombination and slow transfer of photogenerated charge carriers impede the photo-oxidation process of NO_x. Herein, the K_0.5Bi_0.5TiO₃ with oxygen vacancies (KBT-O) realized the enhancement of charge separation caused by the effect of spontaneous polarization. In addition to spontaneous polarization, oxygen vacancies introduced intentionally under UV light irradiation act as hubs for capturing the photogenerated electrons to further enhance the separation of charge carriers due to a surface local electric field. Oxygen vacancies can also serve as active sites to enhance the adsorption of NO and O₂. In particular, the built-in electric field in the KBT-O because of spontaneous polarization improves the separation efficiency of photogenerated charge carriers, resulting in an increased removal rate of NO (53.6%) and a reduced concentration of formed NO₂ (2.1 ppb). This work unravels the important role of spontaneous polarization along with oxygen vacancies in enhancing the deep oxidation of NO over ferroelectric KBT-O photocatalyst under visible light irradiation.