Electronic structure and water induced phase transformation in layered perovskite-like K2La2Ti3O10 photocatalyst for water splitting studied by DFT

Abstract

Layered perovskite-like oxide K2La2Ti3O10 is a perspective photocatalyst for water decomposition at ultraviolet irradiation. In this paper using a density functional theory approach electronic structures of dehydrated and hydrated phases of K2La2Ti3O10 have been studied. It has been found that the water induced phase transformation from I4/mmm to P4/mmm occurs in two steps: at first an increase in the distance between the perovskite layers prevails, and then a shift of the perovskite layers occurs with a moderate changing of the interlayer distance. The band structure calculations have done using the modified Becke-Johnson potential show that K2La2Ti3O10 exhibits indirect band gap of about 3.1 eV. The valence band maximum potential is located at 2.23 eV (vs. normal hydrogen electrode), while the conduction band minimum potential is at −0.91 eV. This confirms the ability of K2La2Ti3O10 both for photocatalytic oxidation of water (producing dioxygen and protons) or pollutants, and to reduce H+ to H2. However, the transfer rate, estimated implicitly from the ratio of the effective masses of the photogenerated holes and electrons in valence and conduction bands, limits photocatalytic performance of K2La2Ti3O10 due to separation ineffectiveness of charge carriers.