Triggering the Channel-Sulfur Sites in 1T'-ReS₂ Cocatalyst toward Splendid Photocatalytic Hydrogen Generation

Electron density manipulation of active sites in cocatalysts is of great essential to realize the optimal hydrogen adsorption/desorption behavior for constructing high-efficient H₂ -evolution photocatalyst. Herein, a strategy about weakening metal-metal bond strength to directionally optimize the electron density of channel-sulfur(S) sites in 1T' Re_{1- x} Mo_x S₂ cocatalyst is clarified to improve their hydrogen adsorption strength (S─H bond) for rapid H₂ -production reaction. In this case, the ultrathin Re_{1- x} Mo_x S₂ nanosheet is in situ anchored on the TiO₂ surface to form Re_{1- x} Mo_x S₂ /TiO₂ photocatalyst by a facial molten salt method. Remarkably, numerous visual H₂ bubbles are constantly generated on the optimal Re_0.92 Mo_0.08 S₂ /TiO₂ sample with a 10.56 mmol g^-1  h^-1 rate (apparent quantum efficiency is about 50.6%), which is 2.6 times higher than that of traditional ReS₂ /TiO₂ sample. Density functional theory and in situ/ex situ X-ray photoelectron spectroscopy results collectively demonstrate that the weakened Re─Re bond strength via Mo introduction can induce the formation of unique electron-deficient channel-S sites with suitable electron density, which yield thermoneutral S─H bonds to realize superior interfacial H₂ -generation performance. This work provides fundamental guidance on purposely optimizing the electronic state of active sites by manipulating the intrinsic bonding structure, which opens an avenue for designing efficacious photocatalytic materials.