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.