Modulating the electronic structures and potential applications of Zr2CO2/MSe2 (M = Mo, W) heterostructures by different stacking modes: A density functional theory calculation

The heterojunctions based on two–dimensional materials have aroused much research interest as they exhibit excellent properties and can be used in various fields such as catalysis, nanoelectronics, and superconductivity. In this study, the typical MXene monolayer, Zr2CO2, was integrated with the MSe2 (M = Mo and W) monolayers to build van der Waals Zr2CO2/MSe2 bilayers with and without twisted angles. The density functional theory (DFT) calculations were conducted at different levels to study the stability, electronic structure, optical absorption spectra, and carrier mobility of the designed bilayers. The BC–stacking Zr2CO2/MSe2 bilayers are energetically favorable and thermodynamically stable. The rotation angle between the Zr2CO2 and MSe2 layers can effectively modulate the band structures by shifting the band edges. The Zr2CO2/WSe2 bilayer with the twisted angle of 46.8° has the flat–like bands in the vicinity of the Fermi level with the bandwidths less than 0.1 eV. The BC–stacking Zr2CO2/WSe2 bilayer (Zr2CO2–WSe2–BC) is a type–II heterojunction with an indirect band gap of 1.44 eV. The valence band maximum and conduction band minimum of Zr2CO2–WSe2–BC are dominated by the electronic states of WSe2 and Zr2CO2 layers, respectively. Zr2CO2–WSe2–BC can be considered a favorable candidate photocatalyst for overall water splitting due to its appropriate band structure, spatial separation of photogenerated carriers, improved response to light, and fast carrier mobility.