First principles modeling of polaron formation and optical signature on titanium-based oxides for oxygen evolution reaction photocatalysis.

The exact mechanism and surface coverage present on (photo)-catalysts used for the oxygen evolution reaction (OER) remain elusive. Ultra-fast spectroscopy on model single crystal surfaces has started to clarify these questions but would benefit from more first principles theoretical support to facilitate the interpretation of the spectroscopic signatures. Here, we focus on the first principles modeling of the optical signature of polarons on OER intermediates on titanium-based photocatalysts (e.g., SrTiO₃ and TiO₂). The trapping of photo-generated holes by polarons on adsorbs at the catalyst surface is a key step in the photo-driven OER. We report from first principles on how the polarons formation process and optical signature changes with adsorbates (OH₂, OH, O) on different surfaces and compare with experimental results when available. Our work is a first step towards a better connection between ultra-fast spectroscopy and first principles computations.