Density Functional Characterization of Pure and Alkaline Earth Metal-Doped Bi12GeO20, Bi12SiO20, and Bi12TiO20 Photocatalysts

Bi12MxO20 +/-delta (hereafter BMO; M=Ti, Si, Ge) materials, which have been used as ferroelectric materials, actuators, capacitors, and dielectric and photorefractive materials, have attracted attention as photocatalysts and exhibit high photocatalytic activities in many reactions. However, seldom has work been performed on the geometric and electronic properties of the BMO structures and little is known about the effect of alkaline earth metal (AE) doping on them. In this study, the pure and AE-doped BMO structures are investigated systematically for the first time by performing first-principles calculations. The electronic structures of the three BMO species show that they should have high diffusion and low recombination rates of photogenerated electron-hole pairs. Alkaline earth ions could easily be doped into the three BMO structures under O-rich growth conditions, and the doping red-shifts the absorption edge of the BMO with its reduction ability unchanged. These new AE-doped materials could