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

In recent years, the semiconductor bismuth oxide (BiO) 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, BiO exists in more than one crystal form and exhibits phase-dependent photocatalytic properties. However, the phase-selective synthesis of BiO is a complex process, and its phase transformation usually occurs in a wide temperature range. Therefore, the development of BiO 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 BiO. 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 BiO is presented in detail. The phase-selective synthesis and temperature-dependent phase stability of highly active BiO are explored. The phase junction in BiO is reviewed, and the future perspective with an outlook on contemporary challenges is provided finally.