Enhanced magnetic and photocatalytic properties of Bi₂Fe₄O₉ semiconductor with large exposed (001) surface

Highlights: • Magnetic Bi₂Fe₄O₉ nanoplates with large exposed (001) surfaces were synthesized. • Highly exposed (001) surface enhances the photocatalytic performance and magnetism. • The mechanisms behind the improved photocatalytic performance are discussed. - Abstract: Magnetic photocatalysts have attracted an increasing attention for photodegradation of organic containments and easy recycling. In this work, magnetic, single-crystalline Bi₂Fe₄O₉ samples have been synthesized through a facile hydrothermal process and the morphologies were modulated by adjusting the Bi³⁺/Fe³⁺ precursor molar ratio and NaOH concentration. The most well crystalline Bi₂Fe₄O₉ nanoplates were formed by self-assembled anisotropic growth along the (001) plane, with large exposed (001) surface. The Bi₂Fe₄O₉ nanoplates exhibit excellent photocatalytic degradation of rhodamine b (RhB) under visible light irradiation with the assistant of a small amount of H₂O₂. The excellent photocatalytic performance of the Bi₂Fe₄O₉ nanoplates was ascribed to the lower recombination rate of the photogenerated electrons and holes on the (001) surface, which was confirmed by detecting the hydroxyl radicals. In addition, Bi₂Fe₄O₉ samples exhibit morphology-dependent magnetic properties. The mechanisms of morphology-dependent magnetic, photoadsorbing and photocatalytic properties of Bi₂Fe₄O₉ crystals are discussed systematically. The magnetic Bi₂Fe₄O₉ photocatalyst allows efficient utilization of solar energy and possible catalyst recovery via magnetically-enhanced gravity separation.