Adsorption on TiO2 is important for applications ranging from catalysis to surface modification of biomaterials. Despite the widespread importance of these processes in industrial applications, the underlying factors in adsorption are not well understood. Experimentally, it is challenging to get a clear geometric and energetic picture of the atomic-level interactions occurring at the adsorbate-substrate interface. Theoretical models provide a way to research these systems and understand the thermodynamic, geometric, and orbital effects of adsorption on TiO2, but these models are not always consistent nor easy to apply. Using meta-GGA density functional methods with localized basis sets, we systematically investigate the effect that computational model size, zero-point energy, and orbital hybridization have on TiO2 adsorption. We find that the adsorption energy, surface energy, lowest-unoccupied molecular orbital positions, and surface atom geometries are strongly dependent on the number of stoichiometric TiO2 layers in rutile (110) slab models. Zero-point energy effects are shown to be insignificant in purely rutile systems, but can shift adsorption energies of CO2 by up to 6 kcal/mol. The Ti-3d(z2) orbitals on the under coordinated 5-fold coordinated titanium atoms on the rutile (110) surface correspond to the lowest unoccupied molecular orbitals in the system, and are the most critical for CO2 binding to the surface. This study can help provide experimental surface chemists with an atomic-level understanding of adsorption to make predictions about favorable adsorbate-substrate interactions, as well as provide theoretical chemists with the tools necessary to develop highly accurate slab models.

Adsorption on rutile TiO2 surfaces: Orbital, zero-point energy, and finite-size effects in theoretical models

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.