MSE Masters Thesis Presentation: Shreyas Dongre

MSE Masters Thesis Presentation: Shreyas Dongre

TITLE: An Electronic-Structure and Adsorption Study of the Rutile TiO₂ (110) Surface

ADVISOR: Sahar Sharifzadeh MSE, ECE

COMMITTEE: James Chapman ME

ABSTRACT: Titanium dioxide (TiO₂) is widely used in photocatalysis due to its chemical stability in air and water, non-toxicity, low cost, and band-edge positions that enable oxidative and reductive reactions under UV illumination. Among its low-index facets, the TiO₂ rutile (110) surface is the thermodynamically most stable and therefore has the lowest surface energy compared to other facets. Its characteristic arrangement of under coordinated titanium and oxygen atoms at the surface provides sites for the adsorption of water and organic molecules, thereby linking surface structure to photocatalytic function. Electronic and surface properties of the TiO₂ rutile (110) surface are investigated using density functional theory (DFT) with the PBE functional. A major limitation of semilocal DFT with the PBE functional is severe underestimation of the band gap, arising from self-interaction errors and the absence of non-local exchange, which leads to overly delocalized Ti 3d states and an incorrect separation between valence and conduction bands. To obtain a more accurate description of the surface electronic structure, a computationally cost-effective Hubbard U correction is applied to the Ti 3d orbitals (DFT+U), partially correcting the self-interaction error and improving the predicted band gap. Rutile (110) slab models of varying thickness are constructed, and their electronic and surface properties are converged with respect to slab thickness. On the electronically converged rutile (110) surface, the adsorption of water and methanol is investigated to determine binding states, preferred adsorption configurations, and adsorption energies. The resulting modifications to the surface electronic structure are analyzed through bandstructure and density of states calculations, which clarify how adsorption on rutile (110) modifies the band edges and their relation to proposed mechanisms for photocatalytic decomposition.