Hydrogen-induced phase stability and phonon mediated-superconductivity in two-dimensional van der Waals Ti 2 C MXene monolayer.

Herein, we report the phase stability of the hydrogenated Ti 2 C MXene monolayer using an evolutionary algorithm based on density functional theory. We predict the existence of hexagonal Ti 2 CH, Ti 2 CH 2 , and Ti 2 CH 4 . The dynamic and energetic stabilities of the predicted structures are verified through phonon dispersion and formation energy, respectively. The electron-phonon coupling is carefully investigated by employing isotropic Eliashberg theory. The T c values are 0.2 K, 2.3 K, and 9.0 K for Ti 2 CH, Ti 2 CH 2 , and Ti 2 CH 4 , respectively. The translation and libration adopted by stretch and bent vibrations contribute to the increasing T c of Ti 2 CH 4 . The high-frequency hydrogen modes contribute to the critical temperature increase. Briefly, this work not only highlights the effect of H-content on the increments of T c for Ti 2 CH x , but also demonstrates the first theoretical evidence of the existence of H-rich MXene in the example of Ti 2 CH 4 . Therefore, it potentially provides a guideline for developing hydrogenated 2D superconductive applications.