First-principles study on the stability, electronic structure, and band alignment of AgNbO3 surfaces: Understanding the adsorption process of H2O and O2

Abstract

In this work, DFT calculations have been employed to delve into the structural, electronic, and optical properties of low-index (010), (100), (101), (110), (011), and (114) surfaces of AgNbO₃. Wulff construction was used to predict the available morphologies of this material and their transformations, which were matched with the experimental images obtained by electron microscopy to support our findings. Our data indicate that the undercoordinated O anions and Ag and Nb cations on these surfaces act as frustrated Lewis base and acid pairs, respectively, to control their structure and electronic properties. These sites at the (110) and (010) selectively bind H₂O and O₂ molecules, opening an energetically favorable pathway for the dissociation of H₂O to enhance the initial stages of the formation of reactive oxygen species, ⋅OH, ⋅O₂⁻ and ⋅OOH radicals, which adsorbed strongly on both surfaces within a simplified model. Overall, the results demonstrate that careful consideration of the impacts of surface chemistry on the behavior of AgNbO₃ surfaces is required to further understand and tailor the reactivity based on the generation of these highly reactive species.