Hydrothermal Synthesis, Photocatalytic and Magnetic Properties of Pure-Phase Bi2Fe4O9 Microstructures

Pure-phase Bi2Fe4O9 microstructures have been successfully synthesized via a facile hydrothermal method without using any organic surfactants. It was found that the synthesis of micro-cubes and micro-plates of Bi2Fe4O9 can be controlled by adjusting the NaOH concentration from 6 M to 12 M, at 200 °C for 12 h, with an optimized Bi/Fe molar ratio of 2:1. With the increase of NaOH concentration, the morphology of the products developed from micro-cubes with a lateral size of 1.5 μm to micro-plates with a lateral size of 1 μm and a curved outline. Moreover, the as-synthesized Bi2Fe4O9 micro-cubes and micro-plates were evaluated for the photocatalytic degradation of methylene blue (MB) under visible light irradiation. A 90% degradation of MB with a time of 120 min has been achieved by using Bi2Fe4O9 micro-plates, where the first-order k constant was determined to be 0.01883 min−1. In addition, these micro-plates exhibit a typical ferromagnetic property at room temperature, offering an opportunity for efficient utilization and recycling via possible magnetic-assisted separation of organic pollutants for photocatalytic degradation.