A review on the preparation, microstructure, and photocatalytic performance of Bi₂O₃ in polymorphs

In recent years, the semiconductor bismuth oxide (Bi₂O₃) has attracted increasing attention as a potential visible-light-driven photocatalyst due to its simple composition, relatively narrow bandgap (2.2-2.8 eV), and high oxidation ability with deep valence band levels. Owing to the symmetry of its unit cell, Bi₂O₃ exists in more than one crystal form and exhibits phase-dependent photocatalytic properties. However, the phase-selective synthesis of Bi₂O₃ is a complex process, and its phase transformation usually occurs in a wide temperature range. Therefore, the development of Bi₂O₃ phases with a controllable microstructure and good photocatalytic properties is a great challenge. Hundreds of articles have been reported on the phase-selective synthesis and photocatalytic performance of Bi₂O₃. However, an interacting and critical review has rarely been reported, and thus it is essential to fill the gap in the literature. In this review, the phase-dependent photocatalytic performance of Bi₂O₃ is presented in detail. The phase-selective synthesis and temperature-dependent phase stability of highly active Bi₂O₃ are explored. The phase junction in Bi₂O₃ is reviewed, and the future perspective with an outlook on contemporary challenges is provided finally.