Density Functional Theory Study on the Role of Ceria Addition in TixCe1–xO₂ Adsorbents for Thiophene Adsorption

A Ti x Ce 1– x O 2 -based material has been reported as a potential adsorbent for ultradeep adsorptive desulfurization of liquid hydrocarbon fuels. To understand the roles of TiO 2 and CeO 2 in the adsorbent, density functional theory (DFT) calculations examined the energetics of adsorption site formation and corresponding thiophene adsorption energies on surfaces of TiO 2 anatase, CeO 2, and Ce-doped anatase. Compared with pure anatase surfaces, thiophene binds more strongly to Ce-doped anatase surfaces. O-rich sites (with activated O 2 ) bind strongly to thiophene, but the formation of the O-rich sites is favored only on higher energy surfaces such as anatase (001) and ceria (100). The formation of a Ti x Ce 1– x O 2 mixed surface decreases the relative surface formation energy of anatase (001), and thus a greater fraction of the (001) facet could be exposed on the adsorbent. Ceria may also act as an oxygen storage reservoir, providing oxygen for the formation of O-rich sites that strongly adsorb thiophenic species.