A Computational Study of Fast Proton Diffusion in Brownmillerite Sr2Co2O5

Solid oxide proton conductor materials are crucial for enabling hydrogen-based energy applications such as solid oxide fuel cells and solid oxide membranes. The improvement in the performance and efficiency of these applications requires the development of novel solid oxide proton conductor materials with higher proton conduction. Recently, brownmillerite Sr2Co2O5 (also known as Sr2CoO2.5) was reported to exhibit exceptionally high proton conductivity at lower temperatures (40-140 degrees C) compared to typical perovskite-based oxide proton conductors. In this study, we perform first-principles calculations to reveal the atomistic mechanisms of proton insertion and diffusion in this brownmillerite structure. By studying hydrogenated brownmillerite Sr2Co2O5 in a range of H concentrations, we reveal the diffusion mechanisms in brownmillerite, which give rise to faster proton diffusion than in perovskite proton conductors. The understanding of fast proton conduction mechanisms in brownmillerite provides insight into the future development and discovery of novel proton conductor materials.