Density functional characterization of Bi-based photocatalysts: BiTaO₄, Bi₄Ta₂O₁₁ and Bi₇Ta₃O₁₈

Using density-functional theory (DFT) calculations, we make a comparative study for the structural, electronic, and optical properties and photocatalysis of triclinic BiTaO₄, orthorhombic BiTaO₄, triclinic Bi₄Ta₂O_11, and triclinic Bi₇Ta₃O₁₈. We predict the photocatalytic capacity by analyzing the band edge position and light absorption. Besides, we calculate the effective masses of holes and electrons to compare the carriers’ mobility of the four bismuth tantalates. The optimized lattice parameters are obtained and crystal structures are analyzed. Electronic properties are studied by analyzing the band structures, partial density of state (PDOS), charge density, Mulliken population, and the hybridization intensity of Bi 6s-O 2p in the valence band maximum (VBM). Optical properties are investigated by calculating the optical absorption coefficient, optical refractive index, optical extinction coefficient, and dielectric function. By comparing the relative ratio of effective mass, we found that triclinic BiTaO₄ and triclinic Bi₇Ta₃O₁₈ not only have excellent mobility of carriers but also have excellent separation of photoexcited electron-hole pairs. Because of desirable mobility and separation of carriers, some absorption in visible light, and suitable redox potential, the four bismuth tantalates are predicted as promising catalyst candidates.