Thermodynamic stability and electronic structure properties of the Bi_2WO_6 (001) surface: First principle calculation

摘要

In this work, using a density functional theory (DFT)-based thermodynamic approach, we studied the stability of possible termination structures for the (001) surface of Bi2WO6. The Bi-W-O surface phase diagrams of the various surface terminations are constructed by obtained surface Gibbs free energies. We find that the five terminations of Bi2WO6 (001) surface can be stabilized under certain thermodynamic equilibrium conditions, though their stability is different significantly. Moreover, based on a hybrid functional, we calculate the five categories of surface termination's surface electronic structures. It is found that there are fat bands of the surface states in O-W termination, which can contribute to visible light absorption. Therefore, an enhanced optical absorption in the visible light region is predicted in the O-W termination. Furthermore, work functions are remarkably distinct for various surface terminations. This suggests that the direct Z-scheme heterostructure of Bi2WO6-based can be controlled by obtaining the thermodynamically preferred surface termination under suitable conditions. These results may help explore intrinsic properties for Bi2WO6 surfaces, providing a useful strategy for experimental studies of Bi2WO6-based photocatalyst in the future.