Photocatalytic water-splitting solar-to-hydrogen energy conversion: Novel LiMoO3(IO3) molybdenyl iodate based on WO3-type sheets

Abstract

The electronic structure of the novel molybdenyl iodate LiMoO3(IO3) based on WO3-type sheets is calculated in order to understand to its usage as a photocatalyst. Using X-ray diffraction data as the initial input, we have optimized the atomic positions by minimizing the force on each atom. Calculations are performed using the generalized gradient approximation (PBE-GGA) within the full-potential linear augmented plane wave method. The optimized structure is used to calculate the electronic band structure and the related properties with PBE-GGA and the recently modified Becke–Johnson potential (mBJ). The top of the valence band (VBM) and the bottom of the conduction band (CBM) are located at the Γ point of the Brillouin zone (BZ), resulting in a direct energy band gap of 2.15eV (PBE-GGA) or 2.73eV (mBJ). It is clear that mBJ succeeds by a large amount in bringing the calculated energy gap into close agreement with the measured one (2.80eV). Thus, LiMoO3(IO3) could be an active visible-light photocatalyst. The angular-momentum-resolved projected density of states reveals that the energy gap value is mainly controlled by O2p (valence bands) and Mo4d (conduction bands) states. The electronic charge density distribution is calculated in two crystallographic planes to explore the chemical bonding characters. The free end Li atom forms ionic bonds, whereas the I atom forms partial valence and dominant ionic bonds with two O atoms. Mo and Li atoms form very weak covalent bonds with O atoms. The calculated chemical bond lengths and angles are in good agreement with the experimental values.