Construction of a α-Bi2O3/α-Bi2O3 homojunction for highly efficient photocatalytic reduction of chromium(vi)

Abstract

A α-Bi₂O₃/α-Bi₂O₃ homojunction composed of α-Bi₂O₃ nanosheets growing on α-Bi₂O₃ nanorods is developed by a facile room-temperature preparation method; this homojunction exhibits significantly high photocatalytic performance for reducing the heavy metal Cr(VI). The degradation of a 50 mg L^–1 Cr(VI) solution under simulated sunlight takes only 6 min, and the apparent rate constant value reaches 0.657 min⁻¹, which is 9.5 times that achieved with the α-Bi₂O₃ nanorods. Photocurrent time curves, electrochemical impedance spectroscopy (EIS) and PL emission spectra prove that the formation of the α-Bi₂O₃/α-Bi₂O₃ homojunction improves the transfer and separation of photogenerated e-h pairs. The average fluorescence lifetime of the α-Bi₂O₃/α-Bi₂O₃ homojunction is 5.1998 ns, which is longer than that of pure α-Bi₂O₃. The results of in situ irradiated X-ray photoelectron spectroscopy (ex-XPS) and the KPFM-based surface photovoltage (SPV) prove that the photoelectrons transfer from the α-Bi₂O₃ nanorods to the α-Bi₂O₃ nanosheet via the interface in light. These findings provide a general and simple synthetic method for preparing homojunction photocatalysts, which has good potential for a broad range of applications.