Effect of the Ti2CTx (Tx = O, OH, and H) Functionalization on the Formation of (TiO2)5/Ti2CTx Composites

Abstract

First-principles density functional theory calculations are carried out on the (TiO2)5 cluster supported on the Ti2CTx(0001) surface with different chemical terminations, i.e., −H, −O, and −OH, to study the interaction and understand the Ti2CTx functionalization effect on the formation of (TiO2)5/Ti2CTx composites. Results show an exothermic interaction for all cases, whose strength is driven by the surface termination, promoting weaker bonds when the MXene is functionalized with H atoms. For Ti2CH2 and Ti2C(OH)2 MXenes, the interaction is accompanied by a charge transfer towards the titania cluster. All adsorptions are accompanied by a significant structural deformation of the titania nanocluster. The analysis of the density of states of (TiO2)5/Ti2CH2 and (TiO2)5/Ti2C(OH)2 composites shows a clear almost metallic character with titania-related states close to the Fermi level. However, for (TiO2)5/Ti2CO2, the band positions are similar to those of a Type-I heterojunction. Overall, the MXene surface termination influence on the TiO2/MXene interaction is unveiled, providing more stable composite formations when the MXene surface is functionalized with −H and −OH groups, where the adsorption process is accompanied by significant charge transfer.