Understanding the impact of structure and composition to the proton solubility in perovskites

In solid oxide proton conductor materials, high proton conductivity is crucial for applications including solid oxide electrolyzer cells and solid oxide membranes. For fast and rational design of novel solid oxide proton conductors, fundamental understanding of how the compositions and crystal structures affect the solubility and diffusivity of protons is demanded. In this work, we use the density functional theory calculations to compute the formation energy of interstitial proton in model perovskite, La_1-xSr_xCoO₃. (0≦x≦1) and its derivatives. First, we consider the connectivity and arrangement of CoO₆ octahedron building blocks using various perovskite structures, such as cubic, hexagonal, orthorhombic, and spinel structures. Next, we substitute La³⁺ ions with Sr²⁺ ions to evaluate the impact of composition and aliovalent doping on the stability of proton interstitials. Our results provide the structure-composition-proton solubility relationship that can be used to identify descriptors for enhancing the proton solubility and integrated with our findings about the impact of these features on proton diffusivity, and materials chemical and electrochemical stability that will be presented in other talks.