Intriguing electronic structures and optical properties of two-dimensional van der Waals heterostructures of Zr2CT2 (T = O, F) with MoSe2 and WSe2

Based on (hybrid) first-principles calculations, material properties (structural, electronic, vibrational, optical, and photocatalytic) of van der Waals heterostructures and their corresponding monolayers (transition metal dichalcogenides and MXenes) are investigated. MoSe2/Zr2CO2 and WSe2/Zr2CO2 heterostructures are found to be indirect band gap semiconductors with type-I and type-II band alignment, respectively, while MoSe2/Zr2CF2 and WSe2/Zr2CF2 are metals. A transition from type-I to type-II band alignment is achieved in MoSe2/Zr2CF2 by moderate compressive and tensile strain. Furthermore, absorption spectra are calculated to understand the optical behavior of these systems, whereas red and blue shifts are observed in the positions of the excitonic peaks under tensile and compressive strain in the heterostructures. Photocatalytic studies show that MoSe2/Zr2CO2 and WSe2/Zr2CO2 heterostructures can oxidize H2O/O-2 to O-2, but unlike their parent monolayers (MoSe2, WSe2 and Zr2CO2) these heterostructures fail to reduce H+ to H-2.