Electron-enriched regulation of sulfur-active site for accelerating atomic hydrogen desorption of S-rich MoWS2+x cocatalyst toward efficient photocatalytic H2 evolution of TiO2

Metal chalcogenides (MSx) as H2-evolution cocatalysts generally suffer from unfavorable H desorption property because of the strong interfacial interaction between the adsorbed H and intensely electronegative S sites (S-Hads, 363 KJ mol−1), which seriously hampers the Hads from desorbing to generate free H2. Herein, a universal strategy of electron-enriched regulation of sulfur-active site is developed to weaken the strong S-Hads bonds by introducing W heteroatoms into MoS2+x to form sulfur-rich MoWS2+x bimetal cocatalyst (expressed as MoWS2+x). In this case, the S-enriched MoWS2+x is skillfully produced and simultaneously anchored with the TiO2 by a facile photoinduced electron-reduction method, involving the aforehand formation of homogeneous W(MoS4)x and their subsequent in-situ photoinduced deposition procedure. Photoactivity experiments exhibit that the MoWS2+x/TiO2(2:1) sample obtains the highest H2-evolution rate of 4620.8 μmol h−1 g−1 (AQE = 22.2 %) with a great promotion of 3.6 folds compared to the MoS2+x/TiO2 sample. In situ/ex situ XPS characterizations and density functional theory (DFT) calculations reveal that the integration of W heteroatom into MoS2+x can regulate its electron density to form electron-enriched S(2+δ)− sites, thus availably weakening the S-Hads bonds to optimize atomic H desorption and accordingly enhancing the hydrogen-evolution activity of TiO2. This study provides a unique idea to optimize the electron densities of activity sites, which is vital for the development of efficient catalytic materials.