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

Abstract

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/Zr₂CO₂ 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/O₂ to O₂, but unlike their parent monolayers (MoSe₂, WSe₂ and Zr₂CO₂) these heterostructures fail to reduce H⁺ to H₂.