Releasing Au Electrons to Mo Site for Weakened Mo─H Bond of Mo 2 C MXene Cocatalyst Toward Improved Photocatalytic H 2 Production.

Mo 2 C MXene (Mo 2 CT x ) is one of the most promising noble-metal-free cocatalysts for photocatalytic H 2 production because of its excellent electron transport capacity and abundant Mo sites. However, Mo 2 CT x typically exhibits a strong Mo─H ads bond, resulting in that the produced H 2 difficultly desorbs from the Mo surface for the limited activity. To effectively weaken the Mo─H ads bond, in this paper, a regulation strategy of electron donor Au releasing electrons to the d-orbitals of Mo sites in Mo 2 CT x is proposed. Herein, the Mo 2 CT x -Au/CdS photocatalysts are prepared through a two-step process, including the initial loading of Au nanoparticles on the Mo 2 CT x surface and the subsequent in situ growth of CdS onto the Mo 2 CT x -Au surface. Photocatalytic measurements indicate that the maximal H 2 -production rate of Mo 2 CT x -Au/CdS reaches up to 2799.44 µmol g -1  h -1 , which is 30.99 and 3.60 times higher than that of CdS and Mo 2 CT x /CdS, respectively. Experimental and theoretical data corroborate that metallic Au can transfer free electrons to Mo 2 CT x to generate electron-enriched Mo δ- sites, thus causing the increased antibonding-orbital occupancy state and the weakened Mo─H ads bond for the boosted H 2 -production efficiency. This research provides a promising approach for designing Mo 2 CT x -based cocatalysts by regulating the antibonding-orbital occupancy of Mo sites for improved photocatalytic performance.