Superconductivity Modulated by Carbonization and Hydrogenation in Two-Dimensional MXenes M₂N (M = Mo, W)

The superconductivity of two-dimensional (2D) materials has extremely important research significance. To date, superconducting transition temperatures (T_c) of 2D superconductors are still far from practical applications. Previously, 2D MXene Mo₂N has been successfully synthesized Urbankowski et al. Nanoscale9 17722, (2017). We systematically investigate the effects of carbonization and further hydrogenation on the stability, electronic property and superconductivity of 1T- and 2H-M₂N (M = Mo, W) based on first-principles calculations. The results show that the 1T-M₂N and 2H-M₂N (M = Mo, W) are all dynamically and thermodynamically stable after carbonization and further hydrogenation. After carbonization, T_c’s of 1T-M₂NC₂ (M = Mo, W) are all increased, while T_c’s of 2H-M₂NC₂ (M = Mo, W) are all decreased. By further hydrogenation, the T_c’s of 1T- and 2H-M₂NC₂H₂ are all increased. Among all of these structures, T_c of 1T-Mo₂NC₂H₂ is the highest one, reaching 42.7 K, and the corresponding electron-phonon coupling strength λ is 2.27. Therefore, hydrogenation is an effective method to modulate T_c’s of 2D M₂NC₂ (M = Mo, W) materials.