Tuning the electronic structure of BaTiO3 for an enhanced photocatalytic performance using cation–anion codoping: a first-principles study

Abstract

Codoping with cations and anions is found to be an effective approach to tailor the electronic structures of semiconductor-based photocatalysts. In this work, a systematic hybrid density functional study has been carried out for BaTiO₃ with a wide bandgap, codoped with TM and X (TM = V, Nb, Ta, Mo and W, X = N and C), with the objective of improving its photocatalytic activity for water splitting under visible light irradiation. Oxygen-rich conditions are found to be more favorable for the synthesis of the (TM + X)-codoped materials, and under these conditions, the formation energy for the codoped BaTiO₃ is even lower than that of the TM-monodoped system. A smaller deformation of the BaTiO₃ crystal structure corresponds to a more favorable formation of (TM + X)-codoped systems. Passivated codoping is found to be advantageous because it effectively reduces the band gap without encountering any localized impurity states observed in the related monodoped systems. The band alignments for all the codoped systems are well positioned for the feasibility of both photooxidation and photoreduction of water. It is found that there are seven investigated systems with bandgaps smaller than 3 eV. Among them, passivated codoped systems including Mo and W have been found to be the most effective for narrowing the bandgap (E_g is in the range of 1.55–2.16 eV), increasing the mobilities of photoinduced carriers and improving the photocatalytic activity of BaTiO₃ under visible light. These materials are promising photocatalysts for overall water splitting under visible-light irradiation and further experimental investigations are highly demanded to explore their potential applications in the photocatalytic field.