Facet-dependent polaron stability in photocatalysis by SrTiO ₃ : a constrained DFT study

Strontium titanate (SrTiO₃ or STO) is one of the promising photocatalysts for sustainable energy applications. Using the density functional theory (DFT) calculations, we herein study the structural and electronic factors contributing to its high photocatalytic activity and facet dependence. The constrained DFT method revealed that the hole polarons in bulk and surface STO are localized primarily on oxygen atoms. In contrast, electron polarons in bulk STO tend to delocalize over oxygen atoms unless stabilized by oxygen vacancies. The stability of hole polarons is higher at the surface O site of the (110) surface compared to the (001) surfaces. In addition, the oxygen vacancy is stable specifically at the TiO₂-terminated (001) surface. These findings provide an atomic-level insight into the relationship between polaron stability and facet dependence of photocatalysis, paving the way for the design of more efficient STO-based photocatalysts.