Controlled synthesis of Bi2NbO5F plates with exposed {010} facet by molten salt method and their photocatalytic mechanism insights

Abstract

Although the preparation of Aurivillius-type oxyfluoride compounds as photocatalysts has been reported, the control synthesis of Bi2NbO5F with the exposed highly active facets is still challenging. Herein, the pure Bi2NbO5F plates have been successfully synthesized through a novel molten salt strategy. Compared to Bi2NbO5F prepared by solid state method (BFS), the Bi2NbO5F obtained by molten salt method revealed better crystallinity and purity. Transmission electron microscope (TEM) and corresponding selected area electron diffraction (SAED) confirm that the main exposed facet of Bi2NbO5F plates is {010} facet. Density functional theory (DFT) calculations indicated Bi2NbO5F crystal belongs to direct-gap semiconductor and its {010} facet was the most active facet due to its highest surface energy. The Bi2NbO5F sample with exposed highly active {010} facet exhibited promoted photocatalytic activity for degradation of tetracyclines (TC) and rhodamine B (RhB) in water as compared to the BFS. The free radical capture experiments prove that O2−, OH and h+ are the main active radicals. The Bi2NbO5F plates with exposed {010} facet still had high photocatalytic activity even after four cycles. Finally, the possible mechanism of Bi2NbO5F nanoplate for photocatalytic degradation of pollutants was proposed.