Reversing Free-Electron Transfer of MoS2+x Cocatalyst for Optimizing Antibonding-Orbital Occupancy Enables High Photocatalytic H2 Evolution

Abstract

The interaction between a co-catalyst and photocatalyst usually induces spontaneous free-electron transfer between them, but the effect and regulation of the transfer direction on the hydrogen-adsorption energy of the active sites have not received attention. Herein, to steer the free-electron transfer in a favorable direction for weakening S−Hads bonds of sulfur-rich MoS2+x, an electron-reversal strategy is proposed for the first time. The core–shell Au@MoS2+x cocatalyst was constructed on TiO2 to optimize the antibonding-orbital occupancy. Research results reveal that the embedded Au can reverse the electron transfer to MoS2+x to generate electron-rich S(2+δ)− active sites, thus increasing the antibonding-orbital occupancy of S−Hads in the Au@MoS2+x cocatalyst. Consequently, the increase in the antibonding-orbital occupancy effectively destabilizes the H 1s-p antibonding orbital and weakens the S−Hads bond, realizing the expedited desorption of Hads to rapidly generate a lot of visible H2 bubbles. This work delves deep into the latent effect of the photocatalyst carrier on cocatalytic activity.