Two-dimensional H-TiO2/MoS2(WS2) van der Waals heterostructures for visible-light photocatalysis and energy conversion

Abstract

Titanium dioxide (TiO2) has promising applications in photocatalysis and energy-conversion devices due to its low cost, outstanding conductivity, and excellent electrochemical activity. However, its large band gap and insufficient-sized surface hinder its applications under visible-light radiation, so designing a highly efficient TiO2-based electrode structure is challenging. Herein, we constructed novel van der Waals (vdW) heterostructures using two-dimensional hexagonal TiO2 (H-TiO2) and 2D MoS2 (WS2) components. By density functional theory, we found that the 2D H-TiO2 has robust stability in energy and mechanics, as well as higher ductility than graphene and MoS2. The estimated indirect band gap ranged within 4.30–4.62 eV, resulting in hardly any visible-light absorbance. The vdW heterostructures of MoS2/TiO2 and WS2/TiO2 had the following characteristics: direct band gap, type-II band alignment, built-in electronic field, mobility as high as that of MoS2 (WS2), and remarkably improved visible-light absorption. These features enabled the heterostructures to have highly improved photocatalytic performance and solar-to-electric power conversion efficiency. Thus, these materials have high potential application in photocatalytic water splitting and solar energy-conversion devices.