Dual role of monolayer MoS_2 in enhanced photocatalytic performance of hybrid MoS_2/SnO_2 nanocomposite

摘要

The enhanced photocatalytic performance of various MoS2-based nanomaterials has recently been observed, but the role of monolayer MoS_2 is still not well elucidated at the electronic level. Herein, focusing on a model system, hybrid MoS_2/SnO_2 nanocomposite, we first present a theoretical elucidation of the dual role of monolayer M0S2 as a sensitizer and a co-catalyst by performing density functional theory calculations. It is demonstrated that a type-Ⅱ, staggered, band alignment of ～0.49 eV exists between monolayer MoS_2 and SnO_2 with the latter possessing the higher electron affinity, or work function, leading to the robust separation of photoexcited charge carriers between the two constituents. Under irradiation, the electrons are excited from Mo Ad orbitals to SnO_2, thus enhancing the reduction activity of latter, indicating that the monolayer M0S2 is an effective sensitizer. Moreover, the Mo atoms, which are catalytically inert in isolated monolayer MoS_2, turn into catalytic active sites, making the monolayer MoS_2 to be a highly active co-catalyst in the composite. The dual role of monolayer MoS_2 is expected to arise in other MoS_2-semiconductor nano-composites. The calculated absorption spectra can be rationalized by available experimental results. These findings provide theoretical evidence supporting the experimental reports and pave the way for developing highly efficient MoS2-based photocatalysts.