Impact of Surface Functionalization on the Electronic and Optical Properties of Ti2C MXenes

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 dimension- ality than the well-researched Ti3C2 , offers a model system. Using density functional theory (DFT) with van der Waals corrections and hybrid functional validation, we thoroughly examine how the physicochemical properties of Ti2C MXenes are affected by four prototypical surface terminations (–F, –O, –Cl, –OH). The thermodynamic stability of all functionalized systems is confirmed by cohesive and formation energy analyses; the lowest formation energies are found in Ti2CO2 and Ti2CCl2 . Dynamical stability across configurations is further confirmed by phonon dispersion cal- culations, which show no imaginary modes throughout the Brillouin zone. Significant differences in work function (2.13–6.30 eV) and quantum capacitance behavior are caused by termination- dependent modulation of the density of states close to the Fermi level, according to electronic structure analysis. The maximum integrated quantum capacitance of 1084.7 µF/cm2 is notably attained by Ti2C(OH)2 , which is explained by enhanced orbital hybridization and extended state availability over the electrochemical potential window. Termination-sensitive dielectric screening is revealed by optical response calculations, which include the infrared-to-ultraviolet spectrum. Our findings provide fundamental principles for the tailoring of low-dimensional materials in electrical and photonic platforms by directly linking surface terminations to emerging quantum and optical phenomena in Ti2C.