Effect for the electronic configurations of LuVO4 induced by D4h crystal-field-splitting discovered in the systematic DFT investigation on photocatalysis capacities of vanadates

Abstract

Vanadates are always a family of promising photocatalytic materials for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). To date, there is lack of systematic research and comprehensive comparison for different vanadates, especially rare-earth vanadates with outstanding optical properties, resulting in ambiguous priority for performance development of different materials. Therefore, crystal structures, optical properties, electronic structures and photocatalysis capacities of twenty-one different vanadates were investigated in details and systematically. AgVO3-C2/m is found to be the most favored in visible-light absorption, while SrVO3-Pm3¯m, LaVO3-Pnma, LaVO3-P21/n, CrVO4-Cmcm and FeVO4-P1¯ are predicted to be competitive in photo-electric conversion. Besides the essential capabilities for driving OER and HER are revealed in the examination of electronic structures, a novel phenomenon is discovered that valence band is mostly contributed by O 2p and Lu 4f states in the band structure of LuVO4-I41/amd, which has been discussed in the framework of crystal field theory, considering Jahn-Teller effects. And it can be described as tetragonal (D4h) symmetry-induced splitting Lu 4f orbitals into five orbitals of closely spaced energies. The incomplete occupation of Lu 4 fz3 orbital induces the metallic ground state and provides the opportunity to adopt donor electrons, driving the HER circle. Furthermore, effect on the electron configurations of V3+t2g2e2 for LaVO3 and V4+t2g1 for SrVO3 induced by Oh and D2h crystal-field-splitting, and the d-d electron transition between orbitals are proposed to provide a novel and essential research route about the photocatalysis capacities of other vanadates.