Enhancement of the Photoelectrocatalytic H₂ Evolution on a Rutile-TiO₂(001) Surface Decorated with Dendritic MoS₂ Monolayer Nanoflakes

The incorporation of two-dimensional MoS2 nanostructures with other semiconductors used in photoelectrocatalytic (PEC) water-splitting for hydrogen (H2) production has been a very promising and eco-friendly approach for providing sustainable clean energy. Herein, atomic-layer MoS2 nanoflakes with tuned morphologies, including dendritic, semicompact, fractal, and compact shapes, are grown by design on a rutile-TiO2(001) single crystal surface via a facile chemical vapor deposition method. The PEC hydrogen evolution reaction (HER) of the MoS2/TiO2 hydride electrodes with four different MoS2 morphologies is comparatively explored. Enhanced PEC HER performance is observed for the composite electrodes, where the H2 production efficiency sequentially increases from the fractal to the compact triangular to the semicompact and finally to the dendritic MoS2 nanoflakes. The mechanism of improvement of the PEC HER efficiency can, on the one hand, be accounted for by the corresponding increase in the effective edge length of the active sites in the MoS2 layer. On the other hand, band realignment at the MoS2/TiO2 interface favors the transfer of the photogenerated electrons in TiO2 to the active sites of MoS2, thereby also leading to enhanced H2 production. The dendritic MoS2 nanoflakes on TiO2, which serve as excellent long-wavelength light absorbers with the enlarged effective edge length as active sites, and the band realignment, which facilitates the migration of the photogenerated electrons onto the active sites of MoS2, play multiple roles in enhancing the PEC HER efficiency for the dendritic MoS2/TiO2 composite electrodes. We hope that this work provides a feasible route toward the development of efficient hybrid HER catalysts.