Construction of an α-Fe2O3/Bi2O3 p–n heterojunction with exceptional visible-light photocatalytic performance for dye removal

Abstract

α-Fe₂O₃/Bi₂O₃ nanocomposites with a p–n heterojunction were synthesized via an anodization strategy and the hydrothermal method for photocatalytic applications. By changing the hydrothermal treatment time, Bi₂O₃ nanosheets were deposited on the surface of α-Fe₂O₃ nanotube arrays (NTAs). The morphologies and photochemical performance of the as-prepared α-Fe₂O₃/Bi₂O₃ nanocomposites were investigated in detail. The presence of Bi₂O₃ nanosheets resulted in an obvious red-shift in the UV-Vis diffuse reflectance spectrum, indicating that the α-Fe₂O₃/Bi₂O₃ nanocomposites had an expanded visible light photo-response range. The α-Fe₂O₃/Bi₂O₃ nanocomposites displayed excellent photocatalytic activity, stability and recyclability toward the decomposition of methylene blue under visible light illumination. The photocurrent and electrochemical impedance spectra also testified efficient electron transport and charge separation in the α-Fe₂O₃/Bi₂O₃ nanocomposites. The enhanced photocatalytic performance can be ascribed to a high light harvesting ability, fast separation of photogenerated electron–hole pairs and the presence of an efficient interfacial electric field from the p–n heterojunction. The photogenerated holes and superoxide radicals played crucial roles in the photocatalytic process. The photocatalytic mechanism was discussed.