Structural, electronic and optical properties of Bi2O3 polymorphs by first-principles calculations for photocatalytic water splitting

Crystal structures of α-Bi2O3 and β-Bi2O3 were calculated using Cambridge serial total energy package (CASTEP) based on the first-principles plane-wave ultrasoft pseudopotential method within local density approximation (LDA) and generalized gradient approximation (GGA) together with Perdew–Burke–Ernzerhof (GGA-PBE) and Perdew–Burke–Ernzerhof revised for solid (GGA-PBEsol). The structural parameter of α-Bi2O3 and β-Bi2O3 are in good agreement with previous experimental and theoretical data. All of the polymorphs were calculated for the total density of states (TDOS) and the partial density of states (PDOS) of Bi, O atoms. Density of states exhibits hybridization of Bi 6s and O 2p orbitals and the calculated charge density profiles exhibit the ionic character in the chemical bonding of this compound. The narrowed band gap (Eg) and red-shift of light absorption edge are responsible for the photocatalytic activity of Bi2O3 for water splitting application. The optical properties such as optical absorption and electron energy loss function were calculated to show the best structure among these polymorphs for the photocatalytic water splitting application.