Interfacial properties of α/βα/β-Bi2O3 homo-junction from first-principles calculations

• Homo-junction is consisted by the α-Bi2O3(101¯) plane and β-Bi2O3 (001) plane.
• The interfacial states are mainly arising from β-Bi2O3 layer at interface.
• The homo-junction of α/βα/β-Bi2O3 belongs to the staggered gaps (type II).
• Photon-generated electron–hole pairs can be spatially separated by homo-junction.

To construct hetero-/homo-junction is an effective way to improve the performance of photocatalyst. However, some basic and important issues about the underlying mechanism of this strategy still need to be further confirmed and explained. In the present work, the interfacial properties of α/βα/β-Bi2O3 composite photocatalyst with homo-junction are in-depth investigated by density functional theory calculations. Owing to partially saturated dangling bonds, the electronic structure of interface model exhibits both the features of bulk and surface models. Importantly, the interfacial states are mainly arising from the layer of β-Bi2O3@Interface. At the interface of α/βα/β-Bi2O3 homo-junction, the energy bands of β-Bi2O3 are relatively down-shifting compared with those of α-Bi2O3, resulting in form the staggered gaps (type II), which is very favorable for the improvement of photocatalytic performance. Moreover, the built-in electric field of homo-junction points from β-Bi2O3 layer to α-Bi2O3 layer under equilibrium, so the photon-generated electron–hole pairs can be spatially separated by the α/βα/β-Bi2O3 homo-junction. Furthermore, to construct α/βα/β-Bi2O3 homo-junction not only keep the advantageous of visible-light absorption of β-Bi2O3, but also improve the visible-light absorption of α-Bi2O3.