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 Ti₂CT_x(0001) surface with different chemical terminations, i.e., −H, −O, and −OH, to study the interaction and understand the Ti₂CT_x functionalization effect on the formation of (TiO₂)₅/Ti₂CT_x 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.