Unveiling the role of surface functionalization in tailoring electronic, optical, and quantum capacitance properties of Ti2C MXenes

Abstract

Surface functionalization has fueled the emergence of Ti-based MXenes as a class of two-dimensional quantum materials with remarkable tunability. When it comes to surface-induced modification of electrical and optical capabilities, Ti₂C, a monolayer version with lower dimensionality than the well-researched Ti₃C₂, offers a model system. Using density functional theory (DFT) with van der Waals corrections and hybrid functional validation, we examine how the physicochemical properties of Ti₂C MXenes are affected by four prototypical surface terminations (–F, –O, –Cl, –OH). The thermodynamic and dynamical stability of all functionalized systems is confirmed by cohesive energy, formation energy, and phonon dispersion analyses. Termination-dependent modulation of the electronic structure influences key properties such as the work function and quantum capacitance, with the latter linked to the density of states near the Fermi level. Optical response calculations reveal termination-sensitive dielectric screening across the infrared-to-ultraviolet spectrum. These results provide fundamental insights for tailoring low-dimensional materials for electronic and photonic applications through surface engineering.