Theoretical Study Of Niobium-based Oxynitride Photocatalytic Materials

BaNbO₂N exhibits light absorption edge up to 740 nm,which is one of the promising perovskite-type metal oxynitride photocatalysts active in 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 including Ba and Nb,respectively.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 the contributions of band edges of surfaces are similar with 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 photogenerated carrier in BaNbO₂N-based heterostructures could be controlled by obtaining the preferred surface termination.Dissociative water adsorption on all the（100）and（001）terminations are thermodynamically favorable.The exposed O atoms are the most favorable sites for HER,especially in cis-（100）-Nb₂O₃N,trans-（100）-Nb O₂and trans-（001）-Ba O.Our results show that cis-（001）-Ba O 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 WO₃and Ti O₂surfaces.Our calculations show a close relationship between the structure and properties of photocatalysts.These findings provide important insights into rational design（100）-and（001）-oriented BaNbO₂N samples for enhanced photocatalytic activity.