Stable Surface Terminations of a Perovskite Oxyhydride from First-Principles

Abstract

Successful synthesis of some perovskite oxyhydrides and their unique catalytic properties have recently attracted researchers’ attention. However, their surface structure remains unclear. Here we identify stable surface terminations of a prototypical perovskite oxyhydride, BaTiO2.5H0.5, under catalytically relevant temperatures and pressures by using first-principles thermodynamics based on density functional theory. Five low-index facets, including (100), (010), (210), (011), and (211), and their various terminations for a total of 47 different surfaces have been examined for relative stability at different temperatures (700, 500, 300 K) and gas environments (10–15 ≤ PO2 ≤ 1 atm, 10–15 ≤ PH2 ≤ 100 atm). The most stable ones are found to be (010)-Ba2O2, (210)-Ti2O2, and (211)-Ba2O4H surface terminations. These polar surfaces are stabilized by charge compensation. This work provides important insights into the stable surfaces of perovskite oxyhydrides for future studies of their catalytic properties.