Selectivity of Adsorption of Thiophene and its Derivatives on Titania Anatase Surfaces: A Density Functional Theory Study

We used density functional theory calculations to examine the adsorption of thiophene and its derivatives (methyl and dimethyl thiophenes) on the (001), (101) and (100) surfaces of titania anatase, of relevance to adsorptive desulfurization of liquid fuels. The adsorption of isomers of methyl and dimethyl thiophenes allows evaluation of electronic, steric hindrance and dispersive attraction impacts on adsorption energies. Adsorption of all species is found to preferentially form a sulfone-like species, where the sulfur containing molecule is partially oxidized on the surface. Oxygen molecules trapped in O-vacancies may serve as the preferred adsorption site for sulfoxide formation. Comparison is made between DFT and DFT-D results, which include a semi-empirical dispersion correction. DFT-D gives a more accurate representation of the interactions between the adsorbate (thiophene) molecules and the adsorbent (anatase) surface. The selectivity of different surfaces towards sulfur-containing molecules is estimated by comparing the adsorption energies of the thiophenes and their corresponding hydrocarbons.