Acid etching followed by hydrothermal preparation of nanosized Bi2O4/Bi2O3 p-n junction as highly efficient visible-light photocatalyst for organic pollutants removal

As a promising visible-light photocatalyst, Bi2O4 has the advantage of broadband spectral response range. However, the high recombination rate of photoexcited charge carriers induced by the submicrorod morphology of pure Bi2O4 greatly restricts its visible-light photocatalytic performance. Herein, a novel nanosized Bi2O4/Bi2O3 p-n junction was developed by a dilute HCl acid etching and subsequent hydrothermal method, using NaBiO3·2H2O as the sole bismuth precursor. A product of NaBiO3·2H2O@BiOCl was formed firstly when NaBiO3·2H2O was partially reduced by insufficient dilute HCl aqueous solution. Then, BiOCl reacted with NaBiO3·2H2O during the following hydrothermal reaction process, resulting in the formation of Bi2O4 nanoparticles (NPs) anchored on the surface of plate-like Bi2O3. The content of Bi2O3 in the junction can be easily controlled by changing the added amount of dilute HCl acid. This strategy could not only realize the NPs-sized Bi2O4 but also construct nanometered Bi2O4/Bi2O3 p-n junction simultaneously, which remarkably improves the separation efficiency of charge carriers. Furthermore, the obtained Bi2O4/Bi2O3 heterojunctions have larger specific surface areas than Bi2O4 alone. Due to these advantages, the photocatalytic removal rate of methyl orange (MO) and phenol for the optimal Bi2O4/Bi2O3 heterostructure increased respectively by 5.06 and 2.16 times under visible light, when compared with single Bi2O4. The results of active species trapping experiment and electron spin resonance (ESR) spectra indicate that holes (h+) and superoxide radicals (O2−) are the primary and secondary reactive active species during the photocatalytic degradation process, respectively. This work provides a novel perspective for the design and preparation of high performance Bi2O4-based photocatalyst.