Theoretical Insights into the Structure, Stability, Electronic, and Photocatalytic Properties of BaNbO₂N Low-Index Surfaces

Abstract

BaNbO2N exhibits light absorption edge up to 740 nm, which is one of the promising perovskite-type metal oxynitride photocatalysts active in the visible-light region. Experiments found that the modification of surfaces and the construction of interfaces on BaNbO2N-based semiconductors are highly related to the photocatalytic performance, but the mechanism is not fully understood. We present here the influence of exposed terminations on the electronic properties and photocatalytic features of trans and cis BaNbO2N using density functional theory calculations. For each surface, we consider two complementary terminations, separately. Analysis of surface energies suggests that (100) and (001) are the most preferentially exposed surfaces among the studied low-index surfaces. Density of states illustrates that the contributions of band edges of surfaces are similar to those of the corresponding bulk. Our calculations reveal that the surface rumpling is highly related to the level of work function. Work functions are distinct for various surface terminations, which suggests that the transferring direction of the photogenerated carrier in BaNbO2N-based heterostructures could be controlled by obtaining the preferred surface termination. Dissociative water adsorption on all of the (100) and (001) terminations is thermodynamically favorable. The exposed O atoms are the most favorable sites for HER, especially in cis-(100)-Nb2O3N, trans-(100)-NbO2, and trans-(001)-BaO. Our results show that cis-(001)-BaO is the most suitable candidate for OER, followed by cis-(100)-Ba2ON. The computed overpotentials for most of the studied terminations are comparable to and even lower than those of WO3 and TiO2 surfaces. These findings provide important insights into the rational design of (100)- and (001)-oriented BaNbO2N samples for enhanced photocatalytic activity.

Perovskite BaTaO2N: From Materials Synthesis to Solar Water Splitting

“…The hydrogen evolution reaction proceeds more easily on the surfaces terminated with Ta, O, and N atoms, while the oxygen evolution reaction proceeds more readily on the surfaces terminated with N atoms than on the surfaces terminated with O atoms. In another work, [ 159 ] they also found that the water dissociation prefers to occur on the BaNbO 2 N surface terminated with N atoms than on the surface terminated with O atoms. Dissociative water adsorption on surfaces with the (100) and (001) terminations is thermodynamically favorable.…”