(262be) Understanding Adsorption on the Anatase TiO2 (101) Surface

Titanium dioxide is one of the most well studied metal oxides due to its wide range of important applications. Of the three structural phases of TiO₂ (rutile, anatase, and brookite), the rutile phase, in particular the (110) surface, has been the most well studied due to its stability and wide availability for study as a prototypical metal oxide; however, the anatase form, which is often the most photocatalytically active form and is adopted by TiO₂ nanoparticles due to its low surface energy, is less well studied. The anatase (101) surface, which comprises the majority of industrial catalysis, is the focus of this particular study. Of particular interest for understanding catalytic behavior of this surface is the study of its fundamental adsorption properties. Adsorption of molecules on the TiO₂ surface often does not readily occur and limits the overall reaction rates and usefulness of catalytic TiO₂. For example, neutral O₂ does not adsorb on (101) anatase TiO₂, limiting the overall rate of photocatalytic organic pollutant degradation, while H₂O forms well-ordered monolayers on this surface. A number of theoretical and experimental studies have been conducted to understand the adsorption of single species on anatase (101) TiO₂, but to our knowledge no single study has conducted a more expansive study of adsorption for a range of molecules to provide a direct comparison of adsorption structures and thermodynamics as well as a fundamental understanding of why some molecules adsorb while others do not. In this work we investigate the adsorption of a wide range of small molecules on the anatase (101) TiO₂ surface using density functional theory (DFT) and develop a fundamental description of adsorption on this important surface.