A 2D ZnSe/BiOX vertical heterostructure as a promising photocatalyst for water splitting: a first-principles study

Abstract

A vertical heterostructure is an effective method for regulating the properties of 2D materials that are superior to their individual components due to the interfacial interaction. Here, 2D ZnSe/BiOX (X = Cl, Br, I) vertical heterostructures as potential photocatalysts for water splitting are systematically investigated using first-principles calculations. The results indicate that the binding strength of the heterostructure is larger than −17.6 meV Å−2, favoring its experimental realization. Furthermore, the phonon dispersion and ab initio molecular dynamics (AIMD) analysis also indicate its good dynamical and thermodynamic stability. Remarkably, the ZnSe/BiOX heterostructures form a type-II band alignment with a direct band gap ranging from 1.78 eV to 2.06 eV, which enables the separation of electrons and holes in two different layers upon visible-light irradiation. The ZnSe/BiOX heterostructures also show high electron mobility, leading to fast migration of photogenerated electrons and extension of their lifetimes. The projected band structure, partial density of states, and partial charge densities show that the electrons of the valence band maximum (VBM) and conduction band minimum (CBM) are located at different sides of the ZnSe/BiOX heterostructures. According to the Bader charge analysis and charge density difference, an internal electric field exists across the interface which will effectively promote the separation of the photoinduced electron–hole pairs. The band-edge positions of the ZnSe/BiOX heterostructures have demonstrated that the band levels of the VBM and CBM stride the oxidation and reduction potential for water splitting. In addition, the band gaps and band-edge positions of the ZnSe/BiOX heterostructures can be tuned by the in-layer biaxial strain. Therefore, our results suggest that ZnSe/BiOX heterostructures are a promising potential application for water splitting under visible light as a novel photocatalyst.