First-principles calculations on the interfacial, electronic and photocatalytic properties of the Ta3N5/SrTaO2N heterostructure

Abstract

The rational design of heterostructures is an effective strategy for enhancing semiconductor photocatalyst performance. In this study, we have employed first-principles density functional theory (DFT) calculations to explore the Ta₃N₅/SrTaO₂N heterojunction, known for its high photocatalytic activity. Based on experimental observations, two distinct Ta₃N₅(110)/SrTaO₂N(001) slab models have been constructed and denoted as Ta₃N₅/Sr₂ON and Ta₃N₅/Ta₂O₃N. Formation energy calculations and ab initio molecular dynamics (AIMD) simulations reveal that Ta₃N₅/Ta₂O₃N exhibits stronger interfacial adhesion due to covalent interactions but is more prone to deformation from lattice mismatch compared to Ta₃N₅/Sr₂ON. Local density of states analysis shows that the band edges Ta₃N₅/Sr₂ON involve atomic layers from both components, while the band edges Ta₃N₅/Ta₂O₃N are solely from Ta₃N₅, potentially enabling more efficient charge separation in Ta₃N₅/Sr₂ON. Both heterojunctions exhibit enhanced optical absorption and a type-II band alignment, with the valence and conduction bands of Ta₃N₅ lower than those of Sr₂ON or Ta₂O₃N by ∼1.2 eV and ∼0.4 eV, respectively, promoting photogenerated carrier separation. Considering the structural stability at room temperature and the consistency of the electronic structure with the desired band alignment, Ta₃N₅/Sr₂ON is a more suitable theoretical model for the Ta₃N₅(110)/SrTaO₂N(001) heterojunction. These findings offer profound insights into the interfacial mechanisms driving the photocatalytic performance of the Ta₃N₅/SrTaO₂N heterostructure and provide essential guidance for designing efficient semiconductor photocatalysts for energy and environmental applications.