Direct evidence of 2D/1D heterojunction enhancement on photocatalytic activity through assembling MoS2 nanosheets onto super-long TiO2 nanofibers

Abstract

Nano-heterostructures (2D/2D, 2D/1D, 2D/0D etc.) have received special attention due to their remarkable performances beyond those of their single-component semiconductor. Direct measurements of the band structure and band bending at the interface of the semiconductors illustrate an important method to understand the fundamental catalytic mechanism and explore promising nanomaterials with improved catalytic property. In this work, the 2D/1D heterojunction with assembling MoS2 nanosheets onto the super-long TiO2 nanofibers is successfully prepared via the electrospinning and hydrothermal method. More importantly, the band bending and electrons transfer of the TiO2/MoS2 heterostructures are directly evidenced by ultraviolet photoelectron spectra (UPS) and in situ irradiated X-Ray photoelectron spectroscopy (ISI-XPS). We find that the as-prepared composite heterostructure exhibited superior photocatalytic hydrogen production activity. Especially, the optimized 2D/1D TiO2/MoS2 heterojunction containing 60 wt% MoS2 showed the highest hydrogen production activity of 171.24 μmoL‧g−1‧h−1, which was about 24 times higher than that of the pure TiO2. To justify the corresponding mechanism of enhanced performance of hydrogen production, photocurrent analysis, electrochemical impedance spectroscopy, ISI-XPS and UPS are also employed to investigate the separation of the photo-generated electron-hole pairs.